Smudge on pictures taken with Nikon d3200?

Here's an example:
It's that dark smudge at the top and center of the photo

I know it's not dirt on the lens since it comes up regardless of what lens I use. So is it just some dirt on the mirror? If so, how should I clean it? If not, what is it; a defect with the sensor? Any help would be very much appreciated because I just bought this camera no more than a week ago for a trip to japan, for which I depart tomorrow! Thank you

Added (1). Okay I just realized I made a dumb mistake thinking it could be dirt on the mirror (it wouldn't show up in the photo then).So is this a defect with the sensor?

Not dirt on the lens

What has happened (and it is hard to do) is you got dust on your sensor.

* Make sure that you have the image sensor cleaning feature turned on
* NEVER change lenses in dusty or windy areas
* Use a "rocket blower" to g e n t l y puff any dust off the sensor. See page 179 to see how to do that
Page 139 tells you how to shoot a dust reference photo until you can clean your sensor properly NOTE: Do NOT touch the sensor.
Dirt on the mirror will NEVER show up on the sensor. As with the sensor NEVER touch the mirror. It is front surfaced and you can damage it by touching it

Note1: Your image has some colour shift. Are you setting your cameras white balance to match the lighting? In this case, for the overcast day?