My toenail turned really white. doesn't itch, no pain. what should i do about it?

Injury or fungus: If you stubbed your toe, or somebody stomped on it, that will do it. If not, the most likely cause is a nail fungus. A dermatologist can do a KOH scraping to see if a fungus is present. Topical antifungals do not cure nail fungus infections - you'll need an oral antifungal like terbinafine or ketoconazole.

Onychomycosis: White superficial onychomycosis (wso) is a fungus which grows on the surface of the nail plate, turning the nail plate opaque and milky white in color. Some forms of the wso infection may well result in opaque whitish-yellowish and at times brown patches on the nail plate.

Fungus: You may have the beginning of a fungus. See a podiatrist for exam and testing of the toenail.