Q&A: Is there any way to get rid of excess skin on my labia?
Labia minora come in various shapes and sizes. Congenitally they can be asymmetrical and have variations similar to the one you mentioned.
With puberty these variations can get exaggerated in some patients. Not knowing your age and without examining you I would be guessing... An anatomical variation, a varicose vein or a papilloma etc.
One answer is simple. You do not have to worry. However, I do recommend talking to your gynecologist and get his or her opinion This will likely put your mind at ease and you could consider removal safely.