It was due to my own carelessness while cutting cardboard with my Rock Lobster. Right over the 2nd knuckle in my left thumb, like a 2 cm cut.
It bled pretty bad but it closed up and stopped bleeding pretty fast once I just stopped moving my thumb and wrapped it good. I can feel it itch a bit so it's healing, it should heal nicely as I had just sharpened my RL the previous day to one of the meanest edges I have ever put on my knives. (I could whittle hair and push cut paper with it... )
MAN did I freak out when it happened, it was like snap, outch and blood. I guess I kinda needed a bit of a reminder.
So remember kids, respect your knives and don't fool around with them, believe me, it sucks living with only one opposable thumb.

And for those of you who are more worried about the knife (I know you're out there :D ), the edge on it after it was undamaged even though it probably hit the knuckle bone.
EDIT:
People demanded pics, here ya go.
Some not-so-pretty pics of the healing cut:


You can see the wound starting from the bloody part and continuing all the way to the side.
Look at that precise straight cut at the side, it's dead straight and has pretty much closed up all the way, now that was sharp!
The top part hasn't closed up yet so you can get a glimpse of how deep it actually was. There also some bruising along the cut so it was quite an impact and hurts if you touch it. :) Enjoy and I hope you weren't eating while you clicked this open. :p