I had a similar looking issue with a festae after she was beaten by her partner. I used Melafix to treat and it cleared right up. No evidence of scarring either. I've also heard good things about Jungle - Fungus Clear.
Stay at the same temp if the box says. I used this a long time ago and it worked. I did lots of water changes and used aquarium after the treatment was done and never saw it again. Good luck.