What Causes A White Lump At The Entrance Of The Vagina?

i have a white bump on the entrance of my asshole its about the size of a pea.. what is it i am really worried that it could be something bad. it doesnt hurt ever. i did try to pinch it a little hard and it feels like fluid a little bit it did hurt a little when i pinched it but pinching anything hurts.. i am a 22 yr old female . please help