I Have A Hole In My Betta

ok so i went to feed my fish this morning like usual and i noticed he wasnt very active.
so i was looking around and he has this huge hole behind his fin i guess near what you would call his stomach
and it was white and not very pretty. he is extremly swollen too.
i tryed my best to take pictures, so pleaseee tell me what this is and what to do about it.

and i think i uploaded them but who knows.

A salt bath would bring down the swelling usually. However not sure how that would feel on his wound.

How are his eating habits? Try feeding some Peas. (Do you know the method for that?)
What all do you feed and how often?
Have you seen him poo lately?

Bad bacteria infection.
Need a very good bacterial med, don't know your location.

http/www.nationalfishpharm.com/articles/aeromonas.html