Ouch! Been there too. Cut my thumb nail in half and cut into the nail bed. Lost the half nail of course. That was 4 months ago and the nail is finally grown. I even use a suction handle...but somehow as I was stretching to make the cut my hand with the rotary cutter jumped the ruler and sliced my thumb! I..am..very..careful..cutting..now. Take care and don't cut too quickly.