Help needed with apparent dust spot on photos

Looking for help. Was out today and took a number of photos with K30 and Sigma 17-70mm 2.8 in various settings, outdoors and inside. Have just looked at them on the laptop and a spot is appearing in the same place in most of the pictures. It is more prominent taken against a blue sky background. I have on start up dust removal on, but I am wondering if it is not the camera, but the lens ( though there is nothing on the glass that I can see ). I have had the lens for about a year and a half, so is still under warranty and the K30 is only a few months old. I am sure there is an easy answer to this and looking to the Forum to those more knowledgeable than myself. Thanks.

You wouldn't see a spot on the lens, so it will undoubtably be a speck of dust on the sensor.

Try the dust removal system several times and if that doesn't clear it try a rocket blower. Make sure to use the rocket blower a few times first to avoid any dust being shot all over the sensor.

If that still is no good then contact cleaning with a swab kit may be needed. But hopefully not.

Another good tip is to pop the flash set the aperture to maximum you can for the lens F22 etc. and shoot at a plain white wall. This will reveal the spots in all their annoying glory, or not, after cleaning.

Thanks to both of you for advice. John, tried the dust removal several times as you said, took a couple of pictures of sky and then of white wall this morning, but dust spot still there. Very annoying as there were some good pictures from yesterday's shoot. Have ordered a " rocket blower ", and hope that will do the trick.