I am thinking by the picture you still have a lens in front of the diode and the contaminate is on the lens. If the lens is in place and you turn it the artifact with rotate with the lens. If it is on the diode window it will remain fixed. I am thinking as well if it was on the diode window it would have already burnt. If you have the means to run the laser at a very low current just over lasing threshold I strongly recommend doing that before powering it to full again.