i thought it was from nose rubbing, because i saw him rubbing hard on his enclosure - turns out to be a symptom, not the cause. no necrotic tissue, just a weird ridge on the inside rim of the teeth on one of the sides of his upper jaw. he's been swollen for about 3 weeks. it got better and worse several times and i thought it was better and i came back and it was absolutely the worst its been so i called the vet.