NIKON AF-S 24-85mm 1:3.5-4.5

I have found that my lens from F9 to F22 has many dust spots. In fact enough to make the images taken at those apertures unsatisfactory. Is there anything I can do? I really don't feel comfortable selling it without being completely truthful about this dust problem and wonder if I should just put it up for sale for parts. I am perfectly satisfied with the images until I hit F11 but this is very limiting. Any advice please. It is definitely not dust on the sensor.