There are dozens of nail diseases and disorders, and a multitude of corresponding treatments. Nail disorders range from simple inflammation to ingrown nails, nail loosening and separation, fungal and/or bacterial infections, psoriatic nails, simple nail trauma, even tumors in the nail matrix.
Nail inspection can give hints to the internal condition of the body as well. Nail disease can be very subtle and should be evaluated by a dermatologist with a focus in this particular area of medicine.