D800: Black spot on sensor

Hi,

I recently discovered a nasty black spot on the sensor of my D800 when taking pictures at f/22 in order to get longer exposure times. The spot is black and relatively large and visible especially at smaller apertures, but all the way down to f/8 if the background is uniform.

I'm not sure if this was there when I bought the camera because the location of the spot is usually cover by details of the landscape and not clear sky, like in the sample pictures below. Also, I usually don't stop down more than f/8 or f/11, so it is harder to detect.

Any idea what this could be and how I get rid of it? I bought the camera in November and it has less than 2000 actuations.

Do I have to send this camera to Nikon for servicing or would that be something that the retailer (B&H) could help me with?

I attached two pictures I took at f/22 and f/11 that show the problem.

f/22:

f/11:



Thanks in advance for any advice!