Hi.. Can understand your concern.. As per your query pain and swelling after dislodgement of post and crown can be due to infection caused below the root tips leading to formation of pus which is causing swelling and pain as after dislodgement of crown and post there has been through and through communication of the internal part of tooth with the mouth.. Other reason can be fracture of the root of the tooth.. Any medication can give a temporary relief and even after medication also some pain can still be present as the exact cause of the problem is still present.. You can take KETOROL DT ( if not allergic) one tablet dissolved in one forth glass of water every four hourly to relieve pain but visiting a dentist and get an IOPAR ( X RAY ) done to find out the exact cause of pain and whether the tooth can be saved by re-doing Root Canal Treatment and Post and core followed by crown or needs to be extracted.. All this can be decided only after clinical examination and x ray. Hope your query is solved.. Thanks and regards.. Dr.Honey Nandwani Arora.