Thank you for the added information,
It is quite likely that the gums around the tooth are sore and are swollen.This could be due to thefilling material that has been used for the core build up or the temporary crown
I assume that the permanent
crown has still not been prepared,and a temporary crown /filling could have been placed by the endodontist[correct me if i am wrong].
The temporary crown /filling could be irritating the gums around the tooth.
It would however be recommended to visit your endodontist/general dentist
to get an Xray to confirm ,if the tooth needs to be treated again.
If the gums are sore because of the temporary crown/filling,then minor adjustments would solve the problem.Cleaning
the gums around the tooth would help in healing and generally reduce the inflammation.
You can take pain killers ,Ibuprofen 400 mg ,if the pain is troubling you.
Warm salt water mouthrinses would be helpful,
Continue using the mouthwash and maintain a good oral hygiene.
Please visit your dentist/endodontist to confirm the exact cause of the problem .
Please let me know if you have any doubts.............