I have 3 and i don't know what one is worse so i'll just state them all.
1. I burnt my arm while making pizza in school. I mean Really burnt my arm. The teacher told me to take the pizza out the oven but she was in the way, so i did the only most normal thing someone would do in this situation, not tell them that they're in the way in instead try to reach the oven door by maneuvering my arm around her legs and trying to open it from there. My arm touched the oven door and that's how it happened. Blisters, Boils, the whole lot. i had to get one of those things that keep your arms in one place on your chest.
2. I jammed my finger in a bathroom door. I wanted to ask my big brother a question and i didn't realise he was in the toilet in time so he panicked and closed the door on my finger, jamming it. I literally had to pry my finger out the door, removing all the skin from the top part. Surprisingly, it didn't hurt nearly as much as it should've
3. We were having a barbeque out in my back garden and i sat behind a window eating our overcooked hot-dogs. When all of a sudden, my big brother (again) opened the window without noticing my head and the window went right into the back of my head. Blood was literally pouring out the back.