Stopped biting my nails with the help of nail polish
A polished nail feels differently in my mouth, which is enough to make me realize I'm doing it and then to stop myself. Here's my current mani vs one of my first
Do! Hope it works for you. For me it made me feel self conscious at first to attract attention to my bitten down nails by colouring them but it was so so worth it! Also now that they're longer, even without polish they feel differently in my mouth than what I'm used to, which is usually enough for me to realize I'm biting too. Good luck to you!
I kicked the habit for years the same way - the different texture of the polish against my upper lip was a perfect reminder. It's amazing just how effective that can be.