It also happens to be an oily area. It is capapable of producing it's own cleansing cycle. You have pores there just like you do on your face. Some times a pore can get clogged and it leaves a small knot. It will either go away on it's own or hurt more and more. If that is the case take very warm baths or showers and warm compresses until the pore opens and drains. Doesn't that sound lovely. It hard work being a female isn't it.