Stoner's Thumb
Any burns substained to your fingers typically being the thumb during the act of smoking cannabis due to the way the light is held. The smoker typically does not care or feel the burn so they continue to burn the cannabis and their thumb.
"Dude I was so high this weekend I got wicked stoner's Thumb"

"Guy1: Bro I think you got stoner's Thumb!
Guy2: Dude Just pass the bong"