How badly is the nail cut? If it' sragged, it might need to be filed some. I remember Tia tore one of nails once, scraed the crap out of me, didn't bother her. I've used Neosporine before on various things, but you might want to put a call into your vet also..
Roxy cracked one of her nails right down the middle and started limping because of it. I had to take her to the vet, she riped off one half of the nail, and gave me some antibiotics to prevent infection and help it heal. It worked very well.