Have one sore red spot on the inner lip of my vagina. It hurt lots initially but is better after a few days. Could it be herpes or would it get worse?

Yes. This could very well be herpes. If you become pregnant it would be very important to have your OB doctor aware of this because it may influence the choice of vaginal vs. C-section delivery. On the other hand this may simply be a clogged gland, another form of std, or other things, and having your doctor examine it is a good idea.
Possible. If the lesion was isolated it is less likely to be herpetic, as they usually come in clusters. That said, it is still possibly herpes. If so, it may return at some point in the same spot. One other possible cause is a small abcess, which can occur in sweat glands, hair follicles or small cysts and usually resolve on their own. See your doctor to consider blood work and evaluation.
Maybe herpes... Sounds like herpes, but can't say for sure. A herpes recurrance goes away after a few days to a week; "primary" herpes laste 2-3 weeks...