Hello & welcome
Type of pain you are presenting here usually occurs in case of some remaining periapical infection, pulp tissue, or any extra canal.
As RCT has been started and tooth is packed with filling, re exploration of tooth is necessary.
In the mean time you can start up with antibiotic course including amoxycilline 500 mg TDS, metronidazole
400 mg TDS, and painkiller ibuprofen
visit your dentist
again and go for check X-ray and re exploration of tooth.
thanks & take care.