I used to have something similar to that on the shaft of my penis. Tiny white, well pearly,spots that looked like they were under my skin. It scared the crap out of me, I knew it couldn’t be STD as I was a virgin at the time (when I went through puberty) and being young I was scared it could be something serious. It turns out though that they are just ‘fordyce’ spots, very common among men and not harmful at all. I believe fordyce spots and pearly white papules are the same thing, not too sure tho, both harmless. Hope that’s helped!