Any surgery can screw up the nerves in the area of the incision (and I imagine the spinal/epidural could as well). I didn't have a c-section, but I did experience what you're describing on my lower leg after a knee surgery years ago. The skin on my shin would alternate between just being numb to a weird feeling like someone was scraping their nails down my leg. I had it on and off for a few months like that and it eventually cleared up as the nerves healed and sorted themselves out. I would mention it to your doctor, but it might just be one of those things that you need to give some time to heal. C-sections are hard on the body, like any major surgery, so you'll need time to recover.