Hi and thanks for the query,
It could really be worrisome for the first time for sure. I think a careful clinical evaluation should be carried out. The duration and evolution of this pimple could be important considerations. Absence of other signs like itches or vaginal discharge
are important too. This could simply be a boil or pus collection, itches a normal immune reaction of the body to contain infection. It could be important for your treating physician to evaluate the condition, to check for associated local symptoms and signs like pain, cervical motion tenderness or presence of associated lymph
nodes. Consulting your physician for a more complete evaluation could be very useful.
Thanks and best regards,