Betta Fish: Suspected cyst but want to double check

Heya,

We've kept this Betta for about 8 months now but recently noticed this cyst/potential tumor developing. His manarisms are still normal, eating totally normal, but of course it does still look concerning.

We've given him anti-bacterial treatment as a precaution incase it bursts, but would really appreciate any insights into what to do for our little guy. Thanks so much!