I would relax. It could be a pimple, and nothing to worry about. I have had them, usually when I am not as clean as I would like. If it does not hurt, I would wait and find out from your dr. But worring about it will probably make things worse. The other thing you can do is take a hand held mirror and have a peak at it. Don't pop it if it is a pimple the dr should do that.
It sounds like it could be a sebaceous cyst: "Sebaceous cysts are usually painless, slow-growing, small bumps or lumps that move freely under the skin. It's important not to touch or try to remove the substance inside to prevent tenderness, swelling, and infection of a sebaceous cyst."
These can form near any sebaceous gland, including the vagina. While they often go away on their own, it is always a good idea to see a doctor when something like this is noticed. Given the size and area of your lump, the doctor may want to try treating you with antibiotics to help it go away.
As ShadowJewels wrote, please do not try to pop it, as this could lead to infection.
Good luck with your doctor visit.