Safe way of disposing resin
Resin is notoriously hard to handle, especially as exposure to air and light can and will cure it over time. The uncured resin is a hazardous material.
Handling hazardous waste
The rules for safe disposal can - generally speaking - be broken down to this:

make sure the hazardous material can't contaminate water or food sources
make sure the hazardous material won't be touched or ingested accidentally

This means (for example for acids) that they are neutralized (to pH 7) and then handled as chemical waste.
WHY?
Why go all these lengths? Let me explain with an example from Germany: The city of Leverkusen is the main site of Bayer. They produce pharmaceutical and chemical products there, which includes a lot of chemical and hazardous waste. Bayer knows how to handle waste, they handled 541000 metric tons globally in 2015. Most of the following information comes from Germany, and is in German, but I do provide my sources.
For the remains of pharmaceutical product production at Bayer in Leverkusen around 2007, the process, as I was told on a tour to the fabrication plant, was generally speaking this: The nasty stuff got neutralized and reacted in ways to make it inert, the resulting sludge got dried and incinerated to destroy most toxic compounds. The remains were bagged in thick plastic bags that were carefully stored with a catalogue of what was stored where in a dedicated chemical waste landfill with (iirc) 3 independent groundwater protection systems, covered with a thick plastic sheet, then with a several meters thick cover of carefully constructed layers of dirt, clay, cement, more plastic, gravel, and rock to protect the rhine and the ground-water. Today, this process is done by the Currenta in a similar way.
In the past, the landfills were less secure: the old landfill that was started by Bayer in 1923 in Leverkusen. It was used by Bayer, the local population and (for some time) the IG Farben. It was finally closed in 1965, contains 65000000 tons of waste, of which approximately 15% is residues of chemical processing (~1 million tons). Nobody ever cataloged what had been stored where in these times, one just knew that it was filled south to north. It had to be pretty much re-engineered in the 1990s and brought it to match the (then) current landfill standard, for example with a 38m deep cement wall: Checks had found that nobody knew anymore where what materials were stored and that residues - among them possibly LOST - had found their way to the surface. These chemicals threatened to get into the Rhine and the water supply at some point. It also lead to a case of public domain and following demolition (for public health concerns) of a group of houses that had been erected on one part of the closed landfill.
You see the length people go to keep you safe from chemical waste: LONG.
Now, how do we fix the problem at hand both safely and effectively?
Getting rid of small batches of resin
The basic rules of handling hazardous waste (the two bulletin points) tell us we should take a two-step process:

find a temporary storage solution (e.g. storing in a safe container)
decide on a process that can get rid of the stuff in a safe way.

How could one fulfill the target number 2? I came up with three options:

re-cycle the unused resin from the print-tub back into the resin for later prints of the same color/resin.
find a specialist to take care of the uncured waste ( =&gt; give it to the waste disposal center in a clearly marked container)
make the material non-hazardous and allow disposal through the home-waste ( =&gt; curing)

Your local waste disposal service might charge a fee for taking care of your resin, but your problems end when you hand it over with old paints or other chemical waste. Check out who provides these services and what laws, rules and regulations apply for small batches of resin and paints.
A different kind of specialist that would take the resin could be a maker or artist that plans to use it in their own SLA/DLP printer.
Making it inert could be done by curing with only sunlight, without the need of much special equipment or chemicals in a very well ventilated area and make sure nobody touches it: pour the resin into a (disposable) mold like a cardboard box or yogurt cup. If you can't have a well-ventilated place, storing the resin in sealed transparent plastic or glass container (plastic bottle or marmalade glasses) in sunlight can cure the resin very slowly over time. Note that it will take quite some extra time, as such containers do filter out some of the 400 nm light that commonly cures the resin.
The resulting resin chunk can be handled like any plastic block once thoroughly hardened through: Use it for other projects, as a paperweight or dispose of it through the normal waste.
tl:dr;

Until you have chosen a method to get rid of your resin, keep hold of it in a sealed container.
You might find a local maker or artist that would like your resin.
The best way to get rid of resin wastes without curing it yourself is handing it to a professional waste disposal service. Check your local laws, code and regulations about it.
Curing it allows disposal through the normal garbage cycle.