i had soreness on my very upper part of my gum. right underneath where my nose would end and when i touch it it's very sore and swollen. my dentist said i needed root canal cergery because my teeth was dead so i did about few days ago. but i still have the soreness on my gum and it's also swollen even more. the pain has not dissappeared at all. if anything it's worse. what can this be?