I went out last night and some black woman slapped me for no reason WTF?

Well I was with my best mate we was elwalling threw town to get a taxi home and some bird came and chatted to me I can't remember what we told each other but this black woman and her mate Starr gobbing of at me and me mate and I stuck up for us and I told them to f off then they both got in me face and saying yo blood ya wanna watch ya mouth i told the black woman to f off back to London considering to Londoner language then I got a slap for me trouble I didn't anything just knocked it on it on the head and walked away now mive bruise on me cheek any advice