I'm not sure whether to be impressed or slightly intimidated by your grandma! Do you have any pictures of your scar?
I've got a couple of scars on my forehead, but both are the pure results of my own stupidity: scar number 1 - I ran into a wall. Scar number 2 - I kneed myself in in the face [whilst trying to do a roll in Aikido - needless to say, I wasn't very good at it].