Left vagina entrance swollen, what should i do?

Bartholin's gland: A swelling near the entrance of the vagina can come from a "Bartholin's" cyst, whose duct that drains lubrication secretions has been clogged. If bacteria get inside the cyst, it can get inflamed and painful. At that point it may help to incise and drain the contents of the cyst. A gynecologic exam will reveal if what I suspect is the case.