After shooting for about a month with my new D7100 I discovered some dust in the viewfinder / focusing screen or the prism area.
The dust is not visible in the images and it does not have any effect on image quality because the dust is not located on the sensor. It's only visible when looking carefully into the viewfinder and you can see a few tiny black spots on the edges of the viewfinder screen. On the Internet this particular issue seems to be quite common.
Is this a normal thing and something I have to get used to when shooting with my D7100?