Well if it's a scratch...I can't see any amount of rubbing getting it out.
If it's a spot on top of the glass....don't spray cleaner directly on to the glass--
if you have to use any cleaner, use it sparingly and spray a bit on a cloth, not on the surface itself.
If it's a wee white spot, sorta in the glass....it could be a stuck/dead pixel.
For those you can have a look at Pixel Fixers--open Google Play and have a search.
There are apps you can download that will (sometimes) fix them if they are stuck.
Dead is dead, in any sport.
If you have alot of them, you may want to return it.