wow, when I was growing up, the way we played it was you would stack your hands on top of the other with the palms facing together and raise your knuckles up on the top hand and you and your partner took turns plucking each other in the knuckles as hard as you could and the first to draw blood won. Good way to pass the time on bus rides from school and I'm pretty sure no one has ever broken their hand doing this.
I would play "quarters". We would take turns shooting them at each other's knuckles. Whoever gave up last, won.
I bled a lot one time, and I still have the scar.
Kids just like to seem tough to their friends, OP. I hope he heals, and that he learned some lesson out of this.
Bloody Knuckles!!! I remember playing that with my big brothers. They must have gone easy on me, because I don't rember any of them having broken my hand.