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You need to see your provider. This has been there for over a year now so it needs proper medical evaluation. I would not apply anything to it or do anything until you've been properly diagnosed.
grace
It looks like dry skin or the beginning of a fungal infection. You should try a moisturizer (one without any chemicals / fragrances that could cause further irritation) and/or a jock-itch cream / spray for a few days. If you don't see an improvement, you should consult with your doctor. Is this the only symptom you have? Has this white patch spread anywhere else?
Have you seen a skin specialist so far?