What would you do, boys fighting!

[Tippytoes13]

Hi, my son goes to football club, which is at the school he goes to once a week. Yesterday my son told me that one of the boys punched, pushed and shouted at his friend, then after he started trying to fight with my son by pushing him, my son retaliated by pushing him back (the other boy, who also was punched and pushed, also pushed him back). The football coach hadn't seen it, so apparently didn't do anything about it. Now, I'm not sure how to deal with this situation, (said boy is often physical) and does do things like this often. I told my son it wasn't right to retaliate and push back, I told him the best thing to do, is walk away and speak to the football coach and tell him what's happened, although they did do that, but apparently he didn't see what happened. Am I right in telling him not to push back, or do you think it was right for him to stick up for himself, (which is what my husband has said). They're 10 years old. How would you deal with it?

Any advice would be appreciated, thanks in advance!