About 5 months ago I underwent a root canal treatment to attempt to save a broken tooth. I was left with a temporary filling until I could be fitted with a crown. Recently I've found a lump, directly above the broken tooth, where the inner lip meets the gum. When the lump is prodded the tooth feels lose, yet there's no pain, just a strange feeling (the same feeling is induced by poking the cheek near the lump.) What could this be?