I think I got a bruise or two while playacting the fight of Gandalf and a (horny) balrog with my friend a few summers ago. (And had I been laughing a bit more, I could have drowned after shouting "fly, you fools!" and letting go of the pier I was gripping.
)
But I don't really have LotR-related injuries. Although I have a lightning-shaped scar (on my finger) like Harry Potter. I guess that doesn't count?