you can add 1 tsp per gallon of aquarium salt if you want to aid in the healing. If you have great water quality, meaning no ammonia, nitrites, and little nitrates then he will heal up fine. All the salt will do is keep infection out and aid in healing. Remember though not to add too much as he is not a salt water fish.
I do recommend adding some aquarium salt as it also adds electrolytes. Follow the instruction on the salt packet and you should be perfectly fine. You should never add treatments unless you know exactly what you are treating for, as most treatments destroy your biological filtration, as I am currently dealing with...
All the best and use the aquarium salt