Thanks for posting your query.
The most likely diagnosis which comes to my mind after going through your history is that it is a Bartholin's cyst
or a Bartholin's abcess. This is a swelling arising from a small gland in your labia majora
due to infection or blockage of it's duct. However nothing can be said for sure until & unless you see a Gynecologist in person & get yourself evaluated. Diagnosis is usually clinical but your doctor may like to take some "swab tests" to rule out the possibility of an STD
Treatment includes a small surgical procedure to open up & drain the contents of the swelling, which is usually done as a "Day case procedure".
However if you have other lumps along with this " bigger one" then other possibilities like STDs or God forbid cancer must be ruled out.
Again a doctors visit is crucial to find out the exact diagnosis.
I have given you a brief guideline please write back if you have any questions.
Wish you good health & a nice day.
Dr. Rakhi Tayal.