I have a bump like a hard small ball form on my inner labia. it has now formed a white head like a pimple. it is sore to the touch but wasn't at first?

Bartholin cyst: It could be a Bartholin cyst or more likely an abscess. You need to see your doctor as it might need to be drained and you may need antibiotics

Poss. Bartholin inf.: This appears to be a possible Bartholin gland infection that may or may not resolve on its own. See a GYN MD if it continues for possible incision and drainage and resolution.