Lump on betta fin

Unfortunately I noticed a lump on my bettas fin that’s only developed today. It’s so large that it’s causing his fin to float and I have no clue what it could be. He still had a good appetite and is swimming around normally. Please someone help!

 

are the water parameters ok? and do you have an airstone/wall? idk what it looks like but there's something called 'air bubble disease' or smth when there's too much oxygen in the tank etc. OR it could be some sort of parasite/bad bacteria? wish i could help

 

are the water parameters ok? and do you have an airstone/wall? idk what it looks like but there's something called 'air bubble disease' or smth when there's too much oxygen in the tank etc. OR it could be some sort of parasite/bad bacteria? wish i could help

Ammonia is 0ppm, nitrites 0ppm, and nitrates 20ppm. He does have an air bubble wall in his tank but I’ve made sure it’s on a really low setting so that the currents not to strong for him to swim through. Thank you for your help, I’ve honestly never seen anything like this

 

It's kind of like a blister on the fin and no one's really sure what causes it. It's harmless and usually goes away on its own.

 

It's kind of like a blister on the fin and no one's really sure what causes it. It's harmless and usually goes away on its own.

Thank you! I noticed this morning it was tiny compared to last night, but now it’s completely gone