Thanks for providing more information.
As per your description and picture suggests possible differential diagnosis like onychomycosis (fungal infection of the nail) and a traumatic blood blister or hemorrhage under the nail without unknown injury.
Your doctor can easily confirm the diagnosis with a simple test called nail clipping for fungal examination. The nail plate can also be sent for fungal culture.
Onychomycosis is best treated with oral antifungals like terbinafine and itraconazole and these require a prescription.
Any traumatic lesion should grow out with the nail and reach the free edge in a few months.
You should keep feet dry and clean.
Wear loose fitted shoes.
Avoid any friction.
Also use abzorb powder if you have excessive sweating and moisture in your feet.
See a dermatologist for further evaluation and treatment.
Feel free for further queries. It's good to discuss rather than quit.
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