It's not the worst thing in the world. But it really isn't great. Fortunately a proper shim or a bar of the proper diameter is an easy remedy.
You may need to remove the bolt and insert a flat blade screwdriver and pry it open a bit to assist installing a new bar or shim.
Whatever you do, don't try to pry it back to original dimensions (whatever that was.) You'll just end up eating into a whatever structural integrity remained. It's never a good thing to permanently reform aluminum. If you are lucky, and the other owner didn't over torque anything, no permanent damage occured in the first place.
I'm leaning towards: "It'll be fine."
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I shouldn't have to "make myself more visible;" Drivers should just stop running people over.
Car dependency is a tax.