Thanks for asking the query,
After a successful Root Canal Treatment the canals are completely devitalised , disinfected so there are no chances of pain .
Pain can be due to incompletely done procedure, re-infection , accidentally left unexplored canal , Take an x-ray which will show left remnant pulp tissue and periapical condition .
Take complete course of antibiotic and analgesic
If the pain is tolerable , you dont worry about the symptoms it will take some days for it to subside . If it persists for more than a month you can consult the Dentist
Hope this helps out.