I've had that before, and this is the blurb that I had saved on my computer about it:
Nail textures: Vertical ridges that appear on the nail can indicate disorders as simple as iron deficiency, poor absorption of vitamins and nutrients, overall poor health or they could indicate something as serious as kidney trouble. (So, you see why consulting your physician is so important.) These vertical ridges, as well as bumpy nails, can also suggest that one is prone to developing arthritis. Ridges running horizontally across the nail can indicate physical or mental stress.
Interestingly, I noticed the ridges during a time in my life when my nutrition was a bit sub-par. With nutritional improvement, I have not seen them since.
CPST ***I can help keep your child safe in the car. Ask me a car seat question!***