I had a cavity filled today. Is it supposed to hurt or cause any discomfort hours afterwards?

not at all or the filling is too high or its in the pulp.

I've had a lot of dental work done and while I've had tenderness of the gums and achy jaw muscles after particularly long work, the only times I've experienced true pain after the filling was under two circumstances: 1) The tooth that was filled needed a root canal or 2) the filling (or crown) was too high and needed to have the "bite" adjusted.

If the pain you're experiencing continues to bother you after 48 hours you should go back to the dentist.

it may be sensitive for a couple of days , your tooth was traumatized by the drilling to remove all unwanted substances and they drill deep sometimes they have to go almost down to the nerve.

yes.