Not sure if how much of a crop you have there... Seriously... I had dust on my D600 when it was new... but cleaned the sensor. All of my friends with DSLRs, Nikons, Canon, Fujis etc. get dust on the sensor... They carry a charge and will attract dust.
I was a bit disappointed that Nikon didn't deliver a pristine sensor but OH well...
That is why there is a multi-million dollar business selling sensor swabs, brushes, magnifiers, and cleaning fluids... to owners of ALL camera brands.
If you can't handle dust then go back ti film... where you get a new sensor with every shot... but then there are the scratches and the dust in the enlarger or scanner... yada-yada yada.