Loos like a dig on the coin. You would have to know for certain whether it's raised or incuse. Easy way to tell is to look at it with a loupe and change the lighting direction and watch the shadow in comparison to something you know is raised. If the shadow is opposite that of the raised element, then it's incuse - a scratch. If it's raised, I agree with Coop - die gouge. It cannot be a die crack....not nearly jagged enough, and it's not in one of the known weak spots for the
Jefferson nickel obverse.