Hello Its good that you are aware of the reason of your teeth problem and you have decided to quit the habit of nail biting. Now talking about the solution to your problem, there are many options ranging from composite laser filling being the most conservative treatment, to veneers and crowns being more invasive ones. But before deciding anything, you need to upload the photographs of your teeth along with x rays to check the intactness of nerve inside the teeth.

The good news is you stopped biting nails...but for the damage that already caused go for a composite restoration to avoid any further dentin damage. Sensitivity will also immediately subside

Hi. As you have mentioned that tooth have reduced in size and its front teeth, it would b clearly visible when u smile or talk. So by doing veneers or crowns in both front teeth your problem of sensitivity and smile, both will b solved.But you wil have to be extra careful when you  bite from that tooth after treatment (since you eat non-veg).

Welcome to Practo. sensitivity can be treated by restoration.  I advise you to do scaling once, do salt water gargling, take Vitamin C supplements the sensitivity will reduce gradually thank you.