Don't use one of those cleaning solutions you see advertised on Amazon,they are meant for LCD screens. Don't go on believing that what works for lcd's works for oled screens. I was warned by the Sony guy who came to my home to do the stand assembly. He said cleaning solutions for oled are not commercially available, the manufacturer authorised service centres have it, those you see available in the market are for lcd's and carry the risk of making a coating peel off on oled, if something wrong goes by using those solutions, Sony won't help you. To clean oled uae a dry folded microfibre cloth . If the stain is tough to remove then use two microfibre cloths, fold them and get one of them a little damp under water, rub the stain in a circular manner and diagonally with the damp one, use the dry microfibre cloth kept next to you immediately and wipe that surface clean, don't wait for it to dry. And when you use the damp microfibre cloth, you should not press into the screen with nails or fingertips , just move it around the surface.