Hello and welcome to healthcaremagic
Judging from your description, I would keep a possibility of
Lichen planus, particularly annular variety of Lichen Planus, which is common on the genitalis.
Clinically there are annular or ring shaped lesions with central clearing/atrophy and a raised rim which is composed of closely set papules of lichen planus. The characteristic of Lichen planus is that the lesions are itchy, planar, purplish and polygonal.
Other sites can be simultaneously affected like
oral mucosa, skin (wrists, abdomen, legs etc). Nail involvement is also very common in Lichen planus
I would suggest that you seek an appointment with a
dermatologist for a confirmatory diagnosis. Diagnosis is clinical.
Treatment of Lichen Planus is commonly with topical steroids like
mometasone propionate, twice daily for a few weeks. Sometimes oral steroids may be required for widespread or diffuse disease.
A OTC antihistamine e.g
cetrizine once daily would help you symptomatically with the itch.
Regards