Using the quick built in sensor cleaning feature only gets some things. I would use the shutter open for cleaning feature in the set up menu and a flashlight to look at the sensor. This things looks much larger than a hair, perhaps a pine needle? If you see something use a rocket blower style brush to try and dislodge it.
The hallmark of stuff up against the sensor is that they are sharper at small apertures and a bit fuzzier at larger openings.
I used flashlight to look at the sensor, didn't notice anything abnormal. I am not an expert, so I might missed it. Will try to take the picture and attach it tomorrow.