Friend help

So at school I was with my friends during lunch. I asked one of my friends for her phone just to play around. I quietly joked that I was going to change her contact names. She half heard what I said and told me to give her the phone. I don't know why but I tried to keep the phone by putting it in my shirt. I was sitting so ( many of my friends)they started tackling me. I was on the ground and one girl stood on my hair. It really hurt. They were trying to get the phone by pulling up my shirt and reaching down it. I was really uncomfortable especially because my ex was standing like 2 feet away from me. I threw the phone against the wall and ran for the bathroom. If this was any other girl (3) I would have the relationship over and done with. But I've know them since kindergarten. What do I do?