If your water conditions are good it should be okay, keep an eye on it for any type of infection and then I would medicate, but usually fins will heal pretty quickly when the water conditions are good and the fish isn't too stressed. If he keeps getting picked on it could get worse. Take a look at my gallery and you can see one of my first fish that had damage to its fin that healed with water changes and a little melafix if I remember correctly. I think melafix is great for injuries that aren't too serious but remember that if you have labrynth fishes it may harm them. I lost a gourami to melafix before I found out.