There might be reinfection in that rct treated tooth causing the trouble & you can visit to the dentist / endodontist.
Next Steps
visit dentist for clinical examination & a small radiographic investigation called iopa of the tooth for confirmation of diagnosis & retreatment.
Health Tips
1.Don't self medicate
2. don't chew from that side till the treatment is done
3.maintain oral hygiene by following proper brushing technique with fluoride containing toothpaste & ultrasoft toothbrush twice daily on a regular basis
4.rinse with lukewarm salt water after every meals to maintain oral hygiene