Old root canal hurting. It's hurts even when I touch it.

Older root canal still hurts. It hurts even to touch it. Had exrays done nothing showed up. Dentist gave me some antibiotics and it cleared up. It will get sore if I chew gum a lot. It is a front bottom tooth. It usually goes away after a day or so. But it's really throbing this time. Dentist said maybe some infection in the root canal said he could go in and scrap it out. But was not 100 % that would fix it. Went for years with no problem but a little soreness. Any hope for this root canal?