What Causes Bump On Labia Majora?

There is a small (like the head of a pin) bump on my labia majora that looks like a tiny blood blister. I have a call in to a gynecologist, but haven't heard back due to power outages in the area and won't be able to get an appointment until a week from now. Any ideas about what this could be, and how urgent it is to be seen by a doctor right away?