What Causes A Fluid Filled Bump On Inner Thigh?

I'm 21 143lbs. I have ovary problems, sinus problems and migraines. I have a lump on my inner right thigh a couple of inches away from my vagina. I wear really tight pants and I'm not sure if that is the reason why I have this lump. It hurts when I walk or when I touch it. It kinda looks like a pimple it sticks out kinda white and purple and soft like if there was liquid in it. What is this lump? How can I get rid of it? Please help!