Hello, thanks for using Health Care Magic. the skin is a harbour for bacterial which in certain cases become harmful to the body. Following shaving, it is very common to have infection of hair follicles that will lead to boils which will be painful. Usually, squeezing to drain the pus is enough treatment though some might want to take antibiotics. It is also possible what you have is an std and more likely herpes. Herpes starts as a small painful blister containing fluid that would burst open to form ulcer. The labia are a common location of herpes genitalia and it is important to rule it out. Thus seeing a doctor to examine the lesion is a better option, mean while if you could abstain at least until the diagnosis is known it could help best regards and hope this helps