Is this sexual assault/harassment?

I don’t know if this is actually sexual assault but I feel violated and upset. I kinda just want to vent. I’m a junior in highschool and the lunch bell rang so I was walking up the steps to go back to class. A group of my guy friends was walking up behind me and I heard them talking but it wasn’t about me. Well this one guy, let’s call him Matt, was joking around to the other guys and smacked one of their asses (as a friend, they all play football) and then they laughed. Well Matt said “let me see your hand” to one of the other guys and was gonna supposedly make him smack a guys butt but instead, he made the other guy smack my ass. The other guy kept apologizing but I’m incredibly mad at Matt and just don’t know what to do. I kinda laughed it off at the time but now I just kinda keep thinking about it all upset and stuff. I know this is nothing compared to other cases of sexual assault but it still upset me.