Hi,
As a previous nail biter, I continuously bit my nails throughout my entire childhood until I was 18 years old. I am now one year free from nail biting. It may not seem like a lot from others' point of view, but for me, it's a huge milestone. I used to bite my nails mainly due to stress and sometimes out of boredom, like when just sitting there doing nothing or watching a movie, etc. I primarily stopped by wearing fake nails or applying nail polish to my fingers. Whenever I would try to bite them, the weird taste or texture would immediately deter me.
Another strategy I used was chewing gum, as it prevented me from biting my nails. I attempted to stop biting my nails throughout my teenage years, but I would often let them grow for a month or so, only to end up biting them again. Consistency is key with whatever method works for you. I've heard some people also use vinegar on their fingernails to deter biting, as it leaves a disgusting taste.
To be honest, everyone in my family was and still is a nail biter, including my 13-year-old brother and my dad. When people commented on my nails, I tended to ignore them, but it did make me feel self-conscious. I would often hide my fingers in pictures and even during class to avoid people asking me about them.