Whose fault is it when...?

I was at a friends house, and i was casually playing ping pong with a friend another friend of mine's (it wasnt his house). The friend, (who i wasn't playing with, whose house it was) jokingly came up to me and started choking me. it wasn't very hard (i could still breathe) but i cudn't exactly see what i was doing. I backed him up to push him in the wall to get him off of me and we busted a huge hole in the drywall. he now expects me to pay for it but i don't think its my fault because i didn't start it. can someone settle this and possibly show me where i can find anything related to this law.