Bartholin's cyst
A Bartholin's cyst, also called a Bartholin's duct cyst, is a small fluid-filled sac just inside the opening of a woman's vagina. The cyst can sometimes affect the outer pair of lips surrounding the vagina (labia majora).
If you have a lump in your genitals, get it checked by your GP. If it turns out to be a Bartholin's cyst and it doesn't bother you, it's often better to leave it alone. Some treatments include soaking it in warm water, incision and drainage, or surgically removing the Bartholin's gland.