An xray is required.
Looks like a case of secondary caries.
Re happening of caries in the same tooth if it was not removed properly the first time or may happen due to a weak filling and improper sealing of the filling material in the tooth cavity during the first time.
If it has not gone deep, a re filling will help ot an rct if the caries is deep.
Health Tips
-Warm salt water rises thrice after taking food.
-Ketorol dt with pan d twice a day for three days if the pain is unbearable. Will give temporary relief.
-Try avoiding biting on the pain side.
-Soft food till you visit a dentist and get it resolved.