Hello, I have gone through your query and understand your concern. I suspect it to be one of the enlarged cyst in the labia majora. Because cysts are the most common cause of swellings in labium majora. These are blocked glands that often swell up and can become painful. Sometimes, they can look like pimples, and you may be tempted to squeeze them to relieve the pain and pressure. This is generally not a good idea because you open up the area to infection from the rest of the vulva. It is better to allow these cysts to open on their own and drain naturally. For large and very painful cysts, it may be necessary to see a doctor for drainage and an antibiotic. But it can also be due to Clogged sweat gland or blocked hair follicle. Without physical examination, it is very difficult to diagnose the cause. Further your blood work up and swab tests are also negative. Thus nothing to worry about this swelling and leave it . Please consult the treating physician, if the swelling is increase in size, any discharge, opens on it own, fever, itching . Hope this helps. Please write back for further queries. Wishing you good health.