I fell off a wall and onto on a broken bottle when I was three, and severed my thumb. It's my best injury and scar. They stuck it back on, but I only have limited movement. It was a genuine accident, in fact, my brother was supposed ot be making sure I didn't toddle out of the garden, so he was in fact the idiot. In spite of this, and many other stupid injuries later, the thing that stings my conscience most is when I was tired and put diesel in the car. A whole freakin' tank full.
Also, with regards to stinging, I have a slightly similar story to Neena's which I wasn't going to share, but will now seeing as she was so brave.
My brother had been in my room and nicked some nail polish remover for paint removal purposes. I had then snatched it from him and thrown the bottle on my bed, without the lid secured properly. I then later, in a naked state, sat on said bed. I just thought it was wet, and jumped up, and as I was wondering what happened to the bed, the burning began. I tried serious rinsing but it still hurt like hell.
I didn't tell anyone, as no doubt my mum would have dragged me off to the doctors for an examination, and as an eleven year old, that was NOT going happen.