Thank you for posting.
If you are not sexually active it's likely a cyst or even a pimple. Sebaceous cysts are less likely to cause pain. A Bartholin's cyst can (sometimes) leak a clear, mucus-like liquid or pus, and in some instances, they're not filled with fluid at all. These cysts can be painful, but they sometimes go away on their own after soaking in a warm bath over a few days. That said, if you're in pain or having trouble sitting or walking correctly, see a gynecologist. They can drain it for you or prescribe antibiotics, depending on what it is after they examine you. If you feel you cannot wait, you can see if there are any walk-in in clinics in your area such as Doctors Express of Urgent Care.