HI, it sounds like a pin worm to me. My sisters and I had them as kids. My mom thinks she got it from a public restroom at the beach and they get under your fingernails and we sucked our thumbs and we got them. They usually come out at night. We took medicine from the doctor and they went away. Never got them since that I know of. You might try what Dr. H. Clark suggests thats the Black-Walnut tinture you put a few drops in water and take the herbs she suggests. The worms can be in your home and bedding etc so use really hot water to wash clothing, bedding, towels etc. Keep fingers out of your mouth. If you have them your kids might have them.