They hardly ever just make a tiny nick and they always seem to do it in a really matter of fact way.
I'm hard as nails but I'm pretty certain I'd try and make as small a cut as possible. I might also hesitate a bit before doing it.
This high quality thread was inspired by my watching The Thing (1982) at the weekend when the characters make two inch incisions in their thumbs to get some blood. Come to think of it, is there a more over-rated film than The Thing?