Hello and welcome to HCM. Thank you for your query. I would have liked to know whether this is present on one side, or on both sides of the vagina. This could most probably be a cyst (a Bartholin cyst; if located inside the vagina), although a physical examination would be the only form of diagnosis, as an online consultation without visualization cannot result in an accurate diagnosis. You could try our paid service and write back to me by attaching pictures of the cyst, if you are comfortable, and I would be more than happy to help. If it is indeed a cyst, it can easily be treated with the help of antibiotics, which will have to be prescribed by a doctor, but if I were to have such a patient, I would advise the use of either metronidazole 500 mg and sitz baths (immersing body in warm water, several times a day). It usually takes about 7-10 days for the cyst to subside. Although treatment and efficacy cannot be guaranteed, as some patients require drainage by a doctor when the cyst does not respond to medical therapy. In the meantime, apply warm compresses and refrain from all forms of sexual contact as this can aggravate the cyst. I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://doctor.healthcaremagic.com/doctors/dr-shoaib-khan/64581 . I would gladly help you. Best wishes.