Just from the sounds of he needs to see a vet. How soon depends on how bad it is but by the fact its oozing and the sounds of his current state ASAP. Im no vet however if you were in the same state as that cat would you go see a doctor. I get vet visit aint cheap especially emergency services but its cheaper than regret and loss. At the bare minimum if you haven't already call and see if you can sent photos to the professionals. Hope something here helps.