welcome to HCM!
most common cause of such pustular eruptions in and around the vagina is bacterial infection,possibility of folliculitis
that is Infection of the hair follicle of the adjacent skin is there.it presents as a pus filled bump (pustular eruption) on the skin.iIn most of the cases, the folliculitis usually is self-limiting but sometimes enlarges and ruptures, discharging the pus. Folliculitis is generally treated with topical antibiotics and antibacterial wash two or three times a day. sometimes may require oral antibiotics
Hope this will help you!take care!