I've had two bad cuts in my 14 months of shaving, both on the crown in almost the same spot. It's that spot right on top in the back that is the hardest part to shave down smooth for some reason. I have to hit that part from multiple angles to get it smooth.
I should probably buy some styptic pencils/powder for those incidents. For those two bad cuts I just put Triple Antibiotic Ointment and a bandage on it. Healed up enough to shave that spot in about 8 or 9 days IIRC.