I’ll hope my response to the template helped you.
Melafix at most can heal abrasions by acting as a mild antiseptic. It’s a mild herbal remedy, so it’s going to do nothing in this situation. It’s also an oil based med, so you don’t want the betta breathing that stuff in.
To lower that
nitrite, do a 50% water change ASAP. You’re going through a fish-in cycle, where the betta is acting as the
ammonia source. As nitrite has appeared, we can know the cycle is progressing.
This might help you:
Tips for fish-in cycling your freshwater aquarium
But yeah, get that cycle done and the betta will begin to heal. He’s in a (literally) toxic environment right now.
When you say “it’s all natural,” what are you referring to?