I have a very painful lump under my skin on my bikini line and has since moved further down between my legs. should i be worried? what causes it?

Needs evaluation: Lumps, bumps, blisters and other skin abnormalities on the genitals need to be evaluated. An examination will be needed to know the cause and treatment. It sounds like you may have a skin infection. Consider a virtual visit where a doctor in your state can visualize via an attached image the area of concern to give a more detailed and more specific answer