Should I tell him I like him?

(On this hike you had to be latched or holding hands with your "buddy" or 2) So there was this night hike the last night of my summer camp and I was with 2 of my best friends. there were no flashlights and it was a new moon so there was only light from stars... So the counselors tell us to go to the side because there was a mud puddle and we had to get in a single file line. well another "friend" of mine (guy) comes up behind me and drags me away from My girl friends looking for his friend. So we got up to His friend near the very front and puts his arm around me, then he puts his arm lower and lower down but I didn't stop him. Then he gets down to my butt and squeezes it. He does it a second time, I'm not stopping him because this is same old thing he does. Then he goes for a third and we were just flirting at this point when his friend sees us and pulls me away from him because he thought it would be a good thing since he is kind of a fuckboy... In a way it wasn't that great getting separated from him but whatever I really like him... So what do I do now? I liked it and I like him a lot so should I ask him out or?!?!?!