Abid Yiddish legal worker for her soul

When I studied the issue, something came to my mind that seemed illogical to me, so I wanted to ask the Rabbi, if my friends and I are walking down the street and someone comes and hits him and injures him, is there a prohibition against me coming and helping my friend by hitting back at the person who is hitting in order to prevent him from injuring my friend? The entire ruling of an Abid Inish is only for himself and not for a stranger.