Thanks for your consult at DoctorSpring.com.
It might have been an ingrown hair, or folliculitis ( infection of the hair follicle root ). When there s such an infection it often heals and forms a fluid filled blister. Tenderness also is a sign of inflammation locally.
Since it is on the way to healing, do not worry. It will scab over and eventually disappear. It's not at all advisable to handle it or touch it. Do not rub / touch / cleanse the area very vigorously. Do not use medicated or perfumed soaps / cleansers / douches / tampons / condoms / toilet paper.
Wear clean, dry cotton undergarments.Avoid keeping the private parts damp. Do not apply witch Hazel locally.
Use local antibiotic cream ( soframycin , beta dine ) . Apply neosporin powder to keep the area dry. It should heal completely in a few days.
Handling it excessively, or bursting blisters , might leave ugly scars behind.
All the best
Please feel free to ask for further clarifications.