Injured big toenail 3 months ago.it was cracked all the way across about a half inch from the cuticle. one side of my nail was completely lifted so i trimmed half of my nail off. the nail bed looks like there is a healed cut/scar. how should i treat?

See dermatologist.: Suggest that you be evaluated by dermatologist for the proper dx and tx. This could be just a result of trauma, but also might be an infection.

Usually regrows: you are seeing the nail bed, which is usually protected by the nail. Most of the time even after a severe injury, the nail will continue growing from the cuticle and push the old nail "off the edge of the cliff". The whole process is 18 months; but usually you can see a band of "normal nail" fully across the cuticle in 3 months. If not, then I would see a podiatrist or dermatologist.