Backstory: me (13F) and let's call her Nyla (12F)

so, it all started when we were at a after school program that has clubs each week for something different so today it was track club, so we just walked around the high school, so my cousin let's call him Hasaun (13) dared me to attempt at touching this sign above this area where you could see the high school gymnasium so I agreed so before I started running I did a quick sweep around to ensure I didn't hurt anybody and Nyla she was in the far right corner so seeing as the sign was in the middle I thought okay its fine Shes not in the way so I'm a short girl (5'2) and the sign is about 7 inches over me so I ran to build some momentum and when I was running Nyla went in the middle so by time I was up in the air touching the sign she was in the middle so when I came down my hand palmed the back of her head pushing her forward so she breaks the side of her glasses and has a scar above her eyebrow due to the impact of my hand.

I'm wondering if I'm the asshole in this situation due to the fact given my age I shouldn't be partaking in dares and what not but at the same time I'm wondering why am I the asshole? because multiple people saw me running/heard me, so it wasn't like I just came out of thin air like the Casper Aswell as the fact I did my due diligent by checking to make sure no one was in the way before I started running, but my cousin included blame me so what do you guys' think AITA?