Oh dear, I'm so sorry. That just SUCKS! I had this happen to one of my favorite fish too, except he was ripped up in the belly and didn't survive.
It depends how severe the injuries are and his own will to survive as well...but MOSTLY the injuries. They can survive some of the worst ouchies though. The other bright side is they also repair damage pretty fast in most cases.
What you want to do is make sure his water stays nice and clean, and stable. The less stress he's under the better, and clean water will help him heal without any infections setting in.
You can try using some stress coat+ to help repair damage and his slime coat faster too. Other than those three things, I don't know of anything else that would help out. Just a stress free area, clean water, and a little something to help repair the slime coat and protect the damaged area so it can grow back fast.
Keep an eye out for infection too. Have some antibiotics on hand, but don't use them unless you have to as meds also stress them out a bit. Clean is the best medicine for this type of thing, but it doesn't hurt to have something a tad more on hand as a just in case.
I hope he repairs and heals up quickly, it's so hard to see them hurting. Please keep us in the loop and let us know what happens. =)