Oh man that looks awful. I would be making a trip to the vet to get some antibiotics right now. Any vet would be capable of doing that whether or not they were reptile experts. I don't know the name of the drug they would give you, but someone will. Once you find out the name and dosage of the medication that is normally given you can ask a vet near you if they can help and tell them what you know. It sort of looks like a mixture of burn and scale rot. The reason I would go to a vet now, regardless of their reptile expertise is because some BPs can't handle infections even when on meds, it's not uncommon to lose them to an infection.