What happened to my Rainbow Fish??

[Christian7]

HI guys, this is my first post on this website.
I have had this bosemanI rainbow for a few years.
A few days ago, I noticed the dorsal fin looked slightly damaged and I figured that it was a self inflicted injury. However, it has been getting progressively worse every day and I'm not sure what it is. I've never had something like this happen to one of my fish and I'm not sure what to do. This fish is the dominant rainbow of the tank (used to often chase others) and is no longer eating anymore.

I have attached some pictures I just took. Any help would be greatly appreciated.

 

[EmbersToAshes]

It looks like a bacterial infection. The wounds have also been contaminated with a fungus. I would set the fish up in a quarintine tank and treat with antibiotics and antifungal medications