Keep the water clean and add salt. I wouldn't feed as much and I would get some good food with garlic like new life spectrum. Feed that to boost immune system. Try some pimafix/melafix for the scrape/wound and to aid your fishes slime coat. If he had a healthier slimecoat that would not happen as easy. What kind of filter are you running? Do you use dechlorinator on tap water? Keep the water clean just dont overclean your tank he needs the beneficial bacteria for his slime coat.