Ouchhhhh! Been there- done that. In my case it was years ago and I was very hot and sweaty. Holding the ruler firmly my L index finger suddenly slid in front of the blade. I heard and felt a Zing sound as the blade hit the bone. Healed quickly since it was such a nice straight cut with a new blade. You might want to get a "birdcage" splint to protect your finger for a while. It looks sort of like a birdcage to shield your wound so nothing but air touches your tender fingertip. Especially handy when sleeping to avoid pain. By now I'm sure you've found keeping your hand elevated helps reduce the throbbing. A sewing coworker cut off a good chunk of her index finger a year ago including the nail and aside from being a little numb it's fine. Hope you heal soon.