Is there anything he can rub on and damage his sublabial scales in his tank? Does the black stuff smell? Looks like it could be mouth rot.
I would use the betadin instead of Neosporin. Betadin is a life saver when it comes to reptiles since you can use it pretty much everywhere and for all wound treatments without much concern for side affects or bad reactions. It also relieves pain. When treating him just make sure he does not rub his snout on anything to much, do not need him making the wound worse.
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