I think you're quite right to assume that friction from sex, tampons, and shaving can produce soreness, especially in a sensitive area like the genitals. The treatment is the same as what you'd do for any other irritation (like dishpan hands)--treat the area gently, and take a break from whatever caused the irritation. Bland ointments like vaseline or any other unmedicated moisturizer are best.
Take care.
Dr. Rockoff