Damn that sucks so bad. I did almost the exact same thing like 2 weeks ago with a filet knife at Irvine Lake. Literaly sliced my finger down the nail all the way down. I just kept it wrapped tight and cleaned it 3 times a day with peroxide and other antiseptics. Its healed now but i have a nasty alil scar and my finger has a bump now on the side. Good luck man, hope it heals soon!