Sick Beta Fish!!! Please Help!!!

[bettafishlover3]

Hello there, I have a sick male Betta fish who is currently around the age of 3. He has devolped a open sore on his top fin. He has lived his life in a 2 or 3 gallon fish bowl with a Betta heater. I'm not sure what is wrong with him or what to do I need some advice. Please help. Thank you

 

[pollex.jaypee]

Emergency solution: Water change.

 

[bettafishlover3]

Thank you pollex.jaypee here are some pictures of my betta so you can get a better look at him

Sent from my SGH-I337M using Aquarium Advice mobile app