Well there are two answers to that tony. Either I bravely fought off a madman with a knife, harming my thumb in the process of saving a damsel in distress.. or I was showing off and it didn't go according to plan.
Tried to cut through the sticker joining two tissue boxes together in one smooth movement. "Watch your thumb!" my brother cried. So I looked at my left thumb, checked it was all safe, and then powered the knife at full speed through the sticker.
He meant the right thumb.