Just keep the water clean. I don't know about a 5 gallon quarantine tank if the cause was a 10 gallon tank making him rub. Hopefully you've got him in an area where he isn't being bothered so he doesn't get spooked at all. Hopefully you can get him into a larger tank soon, I think it'd help him heal quicker (as long as he doesn't have any aggressive tankmates picking on him).
Should be an awesome fish, good luck!!