Thanks for asking the query,
After sucessful Root canal treatment
the canals are completely devitalised, disinfected so there are no chances of pain. Pain in tooth along with swelling in the form of lump indicates infection of the tooth had spread to the periapical tissues leading to formation of abscess.
I would suggest you to consult your Dentist
and get an x-ray done.
Pain can be because of re-infection, incompletely done procedure, accidentally left over unexplored canal, depending upon clinical and radiological examination the treatment can be re-RCT or extraction of tooth.
Take tab amoxiclav
625mg twice , tab Zerodol
TDS for five days,
If having accidity take tab rabeprozole 20mg twice daily half hour before meals.
Maintain a good oral hygiene
, use lukewarm saline gargles, antiseptic mouthwash gargles.
Hope this helps out.