Thank you for submitting your question. There are a few possibilities here. If the bump is the size of a marble and painful to touch, you may have a bartholin gland cyst(this gland is located at the opening of the vagina). If the bump looks more like a popped pimple, then this may be folliculitis(infected hair follicle). Herpes lesions tend to be fluid-filled, and are associated with large lymph nodes in the groin area.
If you think you have a small bartholin gland cyst, in most cases warm compresses three to four times a day should help resolve the swelling. Folliculitis can also be easily treated with topical antibiotic. Herpes would require oral antiviral medication.
If you are concerned about herpes, you should seek medical attention. Blood test is available to check you have herpes. However, from your description I doubt that this is herpes. Herpes lesions are usually very painful and the person usually feels sick(low grade temp).
I hope this answers your question.