On my second D600: Broken diopter adjustment

Looking at the D600 Manual (RTFM?) I find:

1 Turn the camera on.
Remove the lens cap and turn the camera on.
2 Focus the viewfinder.
Rotate the diopter adjustment control until
the AF area brackets are in sharp focus. When
operating the diopter adjustment control with
your eye to the viewfinder, be careful not to
put your fingers or fingernails in your eye.

Could it be that the OP did stick his finger or fingernails into his eye, and that it is this that stops him getting a clear view through the viewfinder?

--
Richard