i'm guessing your nails are short from biting..
so level them out with clippers, get a nail buff and smooth
out all the bumps etc..make them all smooth and even,
then paint them with clear, keep doing this routine once a week/2 weeks
and keep them cut to a reasonable length, also you can get some nail strengthening clear varnish (sally hanson does one) they'll get strong
and harder to bite and they'll look nice too (extra incentive not to bite)