Oooh, ouch. I did that once with a serrated knife, trying to cut the top off of a can of Comet which had gotten waterlogged (brilliant!!!), but since I'm a lefty it's on the other hand. Same finger though! I hope yours heals without any long-term trouble, mine did. I have a circular scar on my fingertip which you can BARELY see (the scar, not the fingertip which is normal-sized :P). The fingerprint grew back, amazingly.