My bite often feels different. It's very likely that I have TMJ.
It could be as simple as adjusting the new filling. Before the dentists dismisses you from your appointment they check your bite but sometimes when people are numb they bite differently than when they're not numb. Even if the filling is off a little bit it can really be irritating.
If your dentist can not adjust your bite properly, you may need to see a prosthodontist. Some people can adapt to newly introduced occlusal interference, some people don't.