My Worst Argument

I've had a lot of arguments in my life but I have to say the worst one I've ever had was with my sister. So one night my mom brought home dinner because she had to go somewhere and she couldn't cook for us. My sister asked for chocolate chip cookies and my mom go them for her. So I asked my sister if I could have one and she said no. However I was really determined to get that Cookie, so when my sister left the dining room and I decided to grab a cookie hoping she wouldn't notice. Unfortunately she noticed, so I ran into my room and she was furious with me. She unlocked the door and she grabbed the cookie out of my hand. Then she started hitting me she punched my stomach and she puounded my head against the wall so many times. Then she grabbed chocolate from the cookie and smeared it all over my face. I was really mad about that because I thought it was really uncalled for, I understand that I shouldn't have taken the cookie in the first place but that didn't mean she had to do all of that. So then I ran out of my room trying to comprehend why she just did that and punched her arm really hard, I was so tired that 30 minutes later I fell asleep. The next morning I woke up with a gigantic bruise on my stomach and it hurt so bad. Something that I learned from this argument is probably that I shouldn't take things without permission, so from now on I won't especially from my sister.