Woah, that does not look good. Is there something (like bedding or anything) stuck to the gum giving it that dark color? Does it appear to be blood/bruising? I ask because those pics make it look dark brown/black to me, which is a sign of necrosis. If it looks black in real life, you need to see a vet immediately. There's nothing that can be done at home for that and things can go south very quickly when tissue is necrotic (and on the jaw that could be fatal).

Do you feed live? If so this could be a feeding injury if the snake took a bite to the face. Did this appear only after the feeding?
If it appears to be blood/bruising from a feeding injury, the situation isn't quite as dire as with necrosis.

Regardless, that is definitely not normal tissue color, and if it isn't already infected I could see it getting infected easily. IMO vet is the best option.