It happens, and it's completely normal. What it is is that a couple of the top layers of the scale (the part that makes it smooth and shiny) get damaged during the shed, usually if they had difficulty shedding the skin, and that part of the scale comes off.

I've had this happen to both my normal and my yellowbelly, and it doesn't harm the snake in any way, shape or form. It should go back to normal in a couple sheds, and it doesn't usually cause further shed issues. Just try to get the humidity up a little higher for the next sheds, and it shouldn't happen again.

Hope this helped