Do Smoked Ham Hocks spoil?
Smoking, which imparts wonderful flavor, is also a preservation method. In fact, that is how it was started. A smoked ham hock will have a low moisture content and long shelf life. Sell by dates are estimates, so this hock is good for quite a while after the date. Remember, too, that a 'Buy before' date then has a shelf life after it.

All that being said, there are official food safety guidelines, then there are the practices that many people use all over the world. A smoked, refrigerated hock should be good for weeks, even months, unless someone is infirm or has weak immune system, or that particular piece of meat is statistically loaded with bacteria. A couple days, a week is totally fine. You can freeze it to extend the life, since it will most likely be simmered for a while when used.

Really it is a choice between going by printed shelf life guidelines and using your judgement and past experience.