Hi,
Without the pics we are guessing to be honest.
It could be a burn or scale rot or some kind of fungal infection.
Did the vet take any swabs of the area to try and find out what is causing it?
Can you tell us what substrate etc you are using and how moist it is and what kind of heat you use and how it is controlled?
Did the vet give you any information as to what he thought was causing it?
He may have put her on anti-biotics simply to prevent infection while the area heals. Did he suggest a non-particulate substrate like paper towels and any cream or ointments to apply to the area?
dr del