One of my kelberi's jumped and hit the cross brace about 6 weeks ago. Top fin was damaged. Came home and found whitish stuff on top fin. She also nicked here face. It looked a little pitted and a little white.
I was freaking! Disease? HITH? From this stress?
I read and calmed down. Solution was to do large water changes and I added salt and Stressguard.
When fish get tissue damage from hitting things or getting attacked their slime coat will aggregate/ build up at the wound. It can have a whitish appearance that can appear to be fungus. So the best thing is frequent and fairly large water changes. The salt can assist with the healing. I have plants so I only added about 3/4 cup in about 120 gal of water. I also like the Stressguard as it really appears to help heal wounds very quick.
So yes Ron is correct but I am just telling the longer story behind this. With any tissue damage clean new water is always #1 IMO.
The damage I see in the photo is minimal. If it were mine I was do water change and Stressguard.
Fungus can always set in if water is not clean and fresh.