Fungal Infected Fish Now Has Huge Wound

[fishman1234]

I just went to feed my danios and my fish that was suffering from a fungal infection but was actually starting to recover now has a massive wound on his back.  I dont have a photo at the moment but it really is a massive injury yet he is swimming just like the others.  What should I do? and the wound really is huge it would be like a human walking around with only half a torso.