There's several knots near my vagina, they feels like the ones you get on your back when your tense; they can move around and are "under the skin"?

Ok: If not painful may be ok. Would consider checking with your doctor

Lymph nodes: they may be small lymph nodes associated with a minor skin infection run the vaginal orifice I would see your physician and let him examine you and determine what they are

Go see a Gynecologis: It is hard to tell what this means unless your physician can examine you. I would advise that you go and see a gynecologist for your peace of mind.