Baby, you get no respect here d ya? You pose a serious question and a couple of the always hovering riff-raff around here swoop down in a feeding frenzy and give utter tripe as so called "advice"! I once suffered from this malady. For years I just couldn't stop from chewing on nails. The one day I was browsing through the local hardware store and spied a box of Phillips #8, 2.5" screws: been chewin on them ever since; never went back to nails. Hope this helps.
as a slight deviation into a serious answer - get gel nail overlays. I bit my nails for approx 30 years, and couldnt stop. I got some fake ones put on for a special occaision and by the time they came off, ny nails were nice underneath, and it made me not want to bite them
It is the roughness and sharp edges of your nails
which is irritating, and which stimulates you to try
to rid yourself of the unevenness of your nails.
Suggestion : buy a small steel nail-file, and
whenever you feel this roughness, just file it till
it's smooth ie. nothing to bite on, or tear.
Always keep the nail-file on your person, ready
for instant action.