Hope your son's eye is o.k. You did the right thing by letting him decide if he wanted to stay there or come home. (Guys have their pride, and probably don't want their mother to come and pick them up in front of their pals.) I remember back when I was a kid, and my two brothers would have reacted exactly the same as your son did. Boys just like to rough-house with one another; it means nothing to them.
Unrelated to the above, but in another post you mentioned a Ganachery; I don't know what that is.