I don’t know what to do

this weekend I went to a party and one of my friends told me that this guy was into me. so we hit it off and we’re cuddling and shit on the couch. he followed me upstairs and grabbed my ass and we started making out. all we did was make out but he did feel me up. he got my snapchat from someone else and now he’s texting me alll the time. i like this guy from my school and we are kind of talking but we aren’t exclusive or anything and I was just trying to get my mind off of him and have fun for a night. I don’t like the guy from the party and I feel bad because I might’ve lead him on or make him think that I was into him when i’m really not. how do I tell him that I don’t like him nicely?