I'm not an expert in camera repairs, but it does look like a hot pixel or two, or three... I would send these sample images to a Nikon service center and ask for their opinion. I suspect they will want the camera shipped for repair (but I don't work for them).
But does it happen all the time or just from time to time? Are the spots always at the same exact spot on the pictures? Do some more testing to determine these facts before contacting them. The more munition you have, the more precise their diagnostic could be.
Good luck and let us know hoe it turns out.