Hi guys, recently i went to a beach to shoot timelapse and then carelessly changed the lens in the midst of strong wind at the beach without much protection for the camera and lens. That's when i spotted dust spots when i was viewing the pictures. Attached is the picture of the dust spots on my sensor at around f22. I used a blower and it got slightly better. I was preparing to clean the sensor by myself but i fear if there are any sand on the sensor which could potentially scratch the glass when i clean it using swabs. Is there any way to differentiate sand and dust particle just by looking at the picture below? If there is sand on it then i might have no choice but to send it to the service centre.