Don't know what you've already done hun, and not trying to preach, just help, but hand in glove with treating it, you need to know what caused it or it may just recur. Usually it's sharp bits on teeth, although could have been thorny shrub bits in the hay, rough edge on the bit etc etc. If he's miserable while you wait for the vet, you could try to pull his tongue out and rinse the ulcer area in warm salty water (so it runs out of his mouth, not down his throat) and then slap some Bonjela on it. Works for me!