I sanded my oak cabinets to put a darker colour stain on them and I guess I sanded them too much in places and the stain won’t take. They look awful. What can I do?

I have a plaster ceiling that I primed. It came out absolutely smooth. I then painted it with a ceiling paint and my roller left behind nap marks over my smooth primed ceiling. Is there any way to restore my ceiling to the smooth surface I had before?