http://www.medhelp.ws/forums/Dermatology/wwwboard.html
They don't seem to be popping up in the proper website
Spooning caused by iron problems or other systemic issues produces the effect on all the nails, not just one. The most common cause of indentation is a thumbnail is the habit of picking at the base of the nail, which irritates the growth area (the white, semicircular part near the base). This causes the nail to have a groove. The treatment is not to pick at the base of the nail. I don't know whether this applies to you, so a visit to a dermatologist would be the way to go.
Take care.
Dr. Rockoff