I have a yellow thing inside my fingernail with a white spot next to it what is is how do i treat it

White spots under: the fingernail are a sign of superficial injury occurring to the nail root, the part under your finger skin before the nail erupts. Perhaps there was some bleeding and resolving blood left a little yellow/hemosiderin tinge. If it doesn't hurt, you can just watch it and wait for it to grow out.It doesn't sound like there is a foreign body/splinter under there, but if you have any question, see Doc.