Reset the camera using "Reset All" in the Setup Menu (see page 75 of your Reference Manual).
If the reset does not resolve the issue, then unfortunately what you have described indicates that there is a problem with the ccd (the light sensitive chip that produces the image)or the connection to it, that was caused by the minor impact.
The information at the link below does fully explain the problem and tells how multiple camera makers handled it. Since more and more newer models have the identical problem the info may give you some leverage with Nikon. You are now the 5th person in a one month period, with a digital camera that I have advised of this problem. Click on or copy and paste the link into your browser
Since your camera is new, if there is no visible physical damage, the Nikon warranty should cover any repair or replacement. A small bump of this type should not cause this problem. You can set up a warranty repair with Nikon at the link below.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well.
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