Plus on top of what banshee here said, you are risking the chance of getting a bacterial infection on any area you piss on an open wound. Yes it is sterile when it comes out but it is a bacterial breading ground after being in the open air. You need to wash it off as soon as possible. The only reason using urine for things such as Jelly Fish stings is because urine is a neutralizing substance. It cuts the acidity of the venom in a sting. It doesn't have the same effects on other instances as this. You are doing yourself more harm then good by urinating on yourself.