Help scratch aquarium glass! Advice needed!!!!

Hey guys I just set up my hex tank got the filter hooked up and
everything and realised that there is a scratch on the outside of the
tank near the bottom..just above the gravel line. I think it happened
today since i've never noticed it before..don't know what could have
done it htough..

What i need to know is...is it still safe to use the tank? It is quite
close to the edge of the glass 2-3 inches from one side and the scratch
is about 0.5 inches long and about i dunno 1mm deep (dunno how to
convert that to inches) so not really deep but you definatly feel it
and you can see it since it is all white.

So can i still use the tank? Do i need to patch it up? How can i patch
it up? This is so sad! right after i bought a canister and spent
50bucks on sandstone and all day setting it up!

Thanks