pain upon chewing is understandable and would be due to inflammation from the
infection (dead nerve) either in the
tooth or in the bone around the
tooth, the bite being off, or a fracture, which my still give you trouble even after the root canal is done and the tooth is crowned. (at that point it may needto be removed) If you were my patient, I'd consider opening and irrigating the tooth with hopes of relieving any pressure from gases (from the infection) in the tooth.