That's not a scratch; it's
patina. If you ride your bike, it will look like it. You'll get used to it. But as
rsbob says, nail polish is the easiest solution.
My newest bike has a rather unusual color that would be hard to match, and so I fill in those nicks with the clear polish that my wife always has around. And I only do that because the frame is steel and I don't want it to rust.