Hi,
Welcome to the ehealthforum and I am glad to help you out. From your symptoms, it looks like a Bartholin's abscess or cyst. There are glands in the vaginal lips called Bartholinâs glands. These can become painful and swollen, and an abscess can form. This often causes blockage in the main duct from the gland, and a cyst develops. This is felt as a painless, hard swelling.
Other possibilities are sebaceous cyst or cyst caused by trauma during sex. You should get a gynecologistâs examination done if the bump persists.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.