Hi...
Pain post Root canal treatment is very normal.As your dentist has said that the RCT is a success, then don't worry.Wait for some more time.
Next Steps
Wait for few more weeks,if it does not subside, then we have to see if there is a crack in the tooth or missed canal .You can get a CBCT done .(only if the pain does not subside after few more weeks)
Health Tips
Do not bite any hard food from the RCT treated tooth ,as there will be higher risk of tooth fracture.