Is it normal to have pain when eating after getting a composite filling?

Sometimes: Placing a composite filling can sometimes lead to temporary discomfort post operatively depending on why the filling was placed. Composites placed to repair deep decay or replace large deep fillings can often traumatize the nerve within. Usually, this pain subsides but in some cases the filling can be removed and an insulating, protective base can be placed under the composite.

Maybe: A filling that is a little to large may cause the pain, it is an easy fix to adjust your bite. If indeed it is due to the filling being deep and the pain remains, you may be in need of a root canal, though, in some cases just replacing the filling may fix your problem too. I would give it some time first to see if the pain settles down on its own, then follow the advice of your dentist.