Dan, I know I'm not being very helpful, but can I ask the question that comes first - why were your friends fighting in a pub, or anywhere for that matter, and calling it 'play'?
And if they are 'mates', and their foolishness led to one being hurt, why is there any suggestion that one will take legal action against the other? 'Mates' don't do that to each other.
You'll get annoyed with me, but I'd suggest a big dose of growing up is needed all round. Let these two sort out their own self-made problems, and steer clear of people who create these sorts of problems by behaving like overgrown babies.