itchy lump/bump on vaginal lips

You should make an appointment as soon as possible. It could be some kind of skin irritation, but you may also be experiencing std symptoms. There are many sexually transmitted diseases that you can carry for years without ever showing symptoms so the fact that you started experiencing this while you weren't sexually active does not mean you should rule out the possibility of an STD.

i have only slept with one person,who has only slept with one other person,but went for a std check and was all clear

Ok, well it's probably not std related then. . . Have you come in contact with anything that may be causing an allergic reaction? New laundry detergent, soap, etc.? Are the lumps symmetrical or are they in different areas? You should probably still go see a professional, but in the mean time you may want to carefully apply some anti itch cream to hopefully relieve the itching until you can figure out the cause. Yeast infection cream would be the most vagina "friendly," but may not relieve the itch since it's formulated for a specific purpose. If you use something like cortizone, just be careful to avoid your urethra and vaginal opening as they can be extra sensitive to harsher creams... hope this is at least a little helpful, good luck.

Oh one other thing. This is really a long shot, but something to think about... Did you notice the bumps in the morning after sleep? It could be some kind of insect bite. Spiders usually bite, then walk and bite again.

you say STD check, how about for herpes, sounds like a soon to be herpes ulscer. go to the doc again soon.
hopefully maybe only allergic reaction or mosquito bite or something innocent.
Herpes though doesnt mean multiple partners, can have it and not ever know, boyfriend could be a carrier.

I have itchy lump between vulva lips.