You have dirt under your fingernails.
- Tu as de la crasse sous les ongles.
Contrary to popular opinion, hair and fingernails do not continue to grow after death.
- Contrairement aux idées reçues, les cheveux et les ongles ne continuent pas à pousser après la mort.
He managed to cure himself of his habit of nibbling his nails.
- Il a réussi à se guérir de son habitude de se ronger les ongles.
Nail polish remover stinks a lot.
- Le dissolvant à ongles pue beaucoup.