I would say that it could be a few things, either knicked while shaving, shaving bumps,abscess, pimple, blisters, warts, STD's, you have glands down there so maybe a swollen gland.
A common cause is a bartholin's gland cyst. This can be a small bump or a very large bump. Some are non-tender, some (when they become infected aka abscessed) can be very painful. A bartholin's gland cyst is caused when the lubrication gland or glands become blocked and the fluid backs up.
bumps on the labia could be a tumor with either benign or malignant nature. however, to sexually active females, bumps on the labia could be a chancre caused by syphillis.
