A similar thing happened to me almost 45 years ago now, and my fingernail went black and fell off (it grew back, I barely 5 years old at the time). To this day, I find black nails on women disgusting.
On the contrary, I (mistakenly) slammed a door from my (now 12-year old) Alfa Romeo to the hand of a relative who was holding on the B-pillar, and it barely touched her hand at all.