On my Nikon D5300, i saw a dust spot I clean the sensor and mirror. It did not go away?

On my Nikon D5300, i saw a dust spot I clean the sensor and mirror. It did not go away?
Added (1). I had a better look. I found that dust speck is inside of camera. Inside side of the focus screen. How do I get this clean? I watched you tube videos of Nikon and canon cameras focus screen been replaced and clean. It looks simple enough. Should I do it or better to take it to a camera shop and let them do it. I KNOW this does not affect the image but its right in the middle of screen so huge distraction.
I am an electronic engineer so i do work with very fragile circuits and steady hands

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