Red dot on pictures taken with D800E

Recently I noticed red dot on three of my pictured taken with Nikon D800E.  Each time dot appears in different areas of the photograph.  Would anyone know what could cause it.  Attached below is the sample - except of the addition of arrow pointing to trouble spot and conversion to small jpg the file is not processed in any way.

Photo details: taken with 50mm prime, 1/640 sec at f /7.1, ISO 200, flash did not fire, manual mode

Thank you in advance for any responses.