Sounds like onycholysis, usually from a nail infection, easily treated.
Here's some info: "Onycholysis is the painless separation of the nail from the nail bed. This is a common problem. It can be a sign of skin disease, an infection or the result of injury, but most cases are seen in women with long fingernails. The nail acts as a lever, prying the nail away from the skin and preventing healing of otherwise insignificant insults. For treatment all of the unattached nail must be clipped off. The hand should be kept out of water as much as possible. Use gloves when cleaning and washing. It is very important to avoid mechanical cleaning under nails. One should not bandage or cover the cut nails. A drying agent such 3% Thymol in alcohol (by prescription) should be used after washing hands or getting hands wet for two or three months. Trim the nails back daily with a clipper until reattachment is seen. Additional medications by mouth may be needed in some cases."