It appears to be fungal, as one of the two tiny holes seems to have white fuzz on it. I have ESHa exit which contains methylene blue, although it is an ich treatment, will that help?
I would try some aquarium salt before medicating your tank. Just dissolve 1 heaped tablespoon of aquarium salt per 5 gallons of water. Just make sure that you dissolve it before putting it in the tank, otherwise it could burn your betta's gills.
I would try some aquarium salt before medicating your tank. Just dissolve 1 heaped tablespoon of aquarium salt per 5 gallons of water. Just make sure that you dissolve it before putting it in the tank, otherwise it could burn your betta's gills.