Was it belted in? If not, did it fly forward with considerable force? Is there any damage to it at all?
Graco has extreme rules about replacement ('any' accident under 'any' circumstances), but for me, personally, I would keep using it unless the crash was enough to injure someone and total the car, because it would take considerable force on the belt path under the armrests for the booster's safety to be compromised. And while you're checking, make sure you used the screws to assemble the armrests properly when you bought it new (they hold the armrests on in a crash when a child is in the seat so the lapbelt doesn't crush the abdomen).
Hope no one was hurt!