Little bump on his side

[snowbell0925]

Hi, this is my first time owning a betta fish and I just got this one a few days ago. I give him three pellets a day, and he's been pretty active since I brought him home, and there doesn't seem to be anything wrong with him. Today I noticed that he has a little bump on his right side, in front of his fin:

can anyone tell me what this is?

 

[LyraGuppi]

It could be a growth, either a cyst or a tumor by what I can see. Usually a fish can still have good quality of life with a tumor. Has his behaviour changed? Does it look cauliflower-esque?