I have a white spot on the inside of my labia, it is not sore but has been there for a very long time, what could it be?

Sebaceous cyst. Most white spots on the labia are sebaceous cysts. These are benign collections of material derived from the skin overlying the labia. If it gets larger or hurts then it needs to be evauated. It most likely will not cause you any problems. However, in postmenopausal women white plaque should be evaluated as they could be precancerous changes.