3D print retouch with soldering iron
I have used a standard soldering iron to modify and fix 3D prints in the past. You have to keep some things in mind when doing so:

Don't overheat your material. PLA can take a soldering iron of about 230 °C before charring.
Don't use a tip with solder, or you will get grey deposits in the plastic.
Round tips or flat tips both work fine, but you want to not dump too much heat into the model or you start to deform the print as it needs to cool again.
Using snippets from the end of the spool for soldering is a good way to recycle the &quot;waste&quot;.