Oh, remember all those movies where people after fighting always grab their hands in pain after the blows? It actually happens a lot to people who never fight and got into one by accident. I suppose that you also don't have fights every other day, so if you want to have strong hands for your upcoming battle, i would suggest that you find a tree/wall/dog/whatever that's strong enough to take a beating and just start hitting it.
No, a punching bags are not good, because they are SOFT. Take a tree or wall and start gently, not too hard but not too light either, enough so that you would feel a bit of pain from every blow. Punch harder if you deem it okay for your hands. After a week, i guarantee your hands will be tough enough for most fights.
Deep into the darkness pearing
Long i stood there
Wondering
Fearing
Doubting.