Depends. We can't see the side view. Is the rim flat at that spot? I agree with the post above, too. Is that a crack or a scratch?
If the rim is flat at that point (or cracked), replace it. You'll have a hop forever.
If it's still round and just scratched, then do as mentioned at the top - Crescent wrench.
EDIT: Just as an FYI, if you send in a wheel to Mavic to be rebuilt, they COMPLETELY rebuild it. New rim, spokes, axle, bearings, and freehub body (if it's the rear). The only thing they re-use is the hub body. How much depends on the dealer. $200-$300 typically for a rear.