Easy peasy as long as it's not deep.
Go to eBay and look for cerium oxide and a rayon pad.
If you have a machine polisher this will be quick and if by hand then a little longer.
Mix the cerium oxide with water to make a paste, apply to the area of the scratch and then polish the scratch with the rayon pad. Don't just do the scratch as this could warp the light through the glass so make it a slightly larger area, done in circles much like polishing paint.
Take your time and it will come right out.