Thanks for sharing your concern.
This is not normal.I think the tooth which has been restored(filled) now after removing the old filling is already infected and also it has involved the pulpal tissue.( site where nerves are located.)
Further the hardness that you are feeling in the jaw, now is the initiation of abscess
around that tooth.
First of all i would suggest you to revisit your dentist
and get your tooth clinically evaluated .also if required get the filling removed.
An x ray
will be helpful along with clinical evaluation.
After that suitable antibiotic and analgesic
can be started.under its coverage RCT can be done and the tooth can be saved.
hope it helps .