Viewfinder on my Nikon D3100 is smudged?

I'm having a weird problem. I can't see clearly out of the viewfinder on my Nikon D3100.
I'm tried cleaning the lens and the viewfinder, but neither work.

Is this something that's common? It's annoying as I prefer that over live view.

Is the picture blurry even when the camera says it is in focus?

it could be because of your diopeter- basically on the side of the viewfinder, you should see a little up and down switch. Toggle it between the different settings until it is in focus.

now if that does not work, it could be that something is smudging the viewfinder, perhaps something got on your mirror?

if that is the case, you might need to send it in to be cleaned.