Try buffing up the water temp to 83ish, and add some extra 02.
If it is hith, the scar will not go away, even once cured. If its just a cut, then it will heal up but still leave a cool scar. My oscar freaked out one time and cut his head open, unfortunatly. Now he has a wicked scar. It healed and scarred over within a week. Healthy fish heal quickly. Hopefully its not HITH, try to take a picture.