Two of my bettas don't have that bump, which is the swim bladder. Both are short finned and quite fleshed-out. My two long-finned, slender-bodied males both had it though.
It isn't parasites.. the lump is nowhere near his belly. It's his swim bladder.
You can see in the 2nd pic below where that is on a betta's body:
I'd say it's pretty normal.
For goodness' sake, don't start throwing parasite meds and antibiotics at him unless he's actually behaving like a sick fish! That's one sure way to make
your fish sick...