AITA for telling a kid not to run up the slide?

I took my daughter (3) to the park and she was really enjoying the slide and kept wanting to go down. It was a double slide so she was going down one side and there was a boy (maybe 11) that was chasing his friends and kept running up the other. On one of the times she went to slide down there was a little girl sitting at the top who was too scared to come down, so as my daughter sat down on the open slide the boy ran up on the side my daughter was on and elbowed her on the side of the head.

Luckily my daughter was not hurt, but she looked scared. When she came down the slide she asked me to tell the boy not to do that, so I told her I would. When he came back around to run up the slide again I blocked the slide with my arm and asked him not to run up the slide because he hit my daughter in the head. He just stared at me so I asked him where his parents were and he pointed somewhere behind me. I looked back but didn’t see anyone looking our way and when I turned back to the boy he bolted towards the the stairs of the slide.

A little later I see him walk towards a women and I ask her if she’s his mother. She nods and I tell her what happened. I do this at a distance because I don’t want to seem threatening. The boy looked at his mother and said that he didn’t hit my daughter and I said “you probably didn’t realize you did it but I saw”.

The mom said “well there were other kids running up too” I said “all I ask is that he not run up when other kids are trying to come down” and she said “makes sense” then looked at her son. I’m not sure what was said between them but at that point I turned to leave since I knew they weren’t going to say anything else to me. Then a minute later I hear him say very loudly as he’s walking away from his mom “that lady is so mean” while crying. I felt bad that I made him cry so I looked at him and said “I’m sorry if I hurt your feelings” and he stomps further away. After that I didn’t see him playing on the playground anymore.

I’ve never had to confront anyone before and I’m feeling guilty that my first time ended up making a kid cry. So am I the A-hole for telling a kid not to run up the slide?