Small, painless lump on labia majora?

It doesn't hurt or itch. It's about the size of a popcorn kernel. It's not on the surface, it's like a few millimeters under the skin. The location is almost flush with my clitoris, and is halfway between the middle of my vulva and my thigh. The coloration is only 1 or 2 shades darker than my natural skin tone. I almost didn't notice it, but I shaved Sunday morning, and noticed it Sunday evening. I don't remember if it was there at the time I shaved or not. Also, there is no "head." Is this a deep pimple, boil, or ingrown hair? Or should I be worried (cancer, etc)? I'm 20, sexually active (although I don't think that pertains to this), and negative for STDs.