Hi there
Hello and welcome, The pain after root canal treatment may be due to-Infected pulp remaining within the canals, Overpenetration of files through the apex. Ledge formation. I would advise you to visit a dentist and get a thorough clinical as well as x-ray examination done. Take complete course of antibiotics-analgesics. Maintain oral hygiene well. Apply cold packs to subside the swelling. Hope this helps.