The bump could be several things depending on where exactly it is. If the bump is truly medium sized, solitary, and adjacent to your vaginal orifice, you may be experiencing a common problem called a Bartholin's gland cyst. It is very difficult to diagnose such things without actually seeing them, so a Bartholin's glans cyst is just one of several possibilities and you really need to see a doctor
and have the area examined for an accurate diagnosis. Bartholin's glands are found on either side of the vaginal orifice and their purpose is to secrete lubricating mucous. Occasionally these glands become blocked and fluid backs up, causing a bump to form on one side of the vaginal orifice. The bump is usually medium sized, solitary, found only on one side of the vagina, and can be slightly tender. Sometimes the trapped fluid in the cyst can become infected by resident bacteria, causing the cyst and the area around it to become inflamed and very tender. Occasionally Bartholin's gland cysts will go away on their own and warm compresses can alleviate symptoms and possibly help the cyst drain. But many times minor surgery
is required to open the cyst, help it drain, and cure the problem. You should visit a gynecologist promptly to see whether you are suffering from a Bartholin's gland cyst, or another problem such as a skin abscess
or a sexually transmitted disease. Regardless of what the problem ends up to be, a gynecologist will be able to diagnose it accurately and offer treatment.