Gear Box Impact

If the prop didn't break and the spinner is only scratched plus the engine wasn't running I'd say you're probably just fine. I'd have a different view if the prop was wiped out and the spinner smashed off. Then I'd want the prop shaft and prop flange checked for true.

It looks like you dodged the bullet!
At a minimum, I would proceed as if you had a prop strike.

Pull the Prop and inspect to see if the spinner struck the prop.
While it is off, check the Prop Shaft Flange Runout.  (HMM 72-00-00; 3.9.10)

If BOTH checks are OK, put it back together.

Hi All

I can tell all that in gearbox impacts the engine need not be running to be damaged.  years ago when we had shipping boxes made of cardboard rather than the current plywood, fork lifts could damage a prop flange.  Even if the flange is not bent I found some that bent the 4 retaining bolts inside that retain the ball bearing from movement.  

My recommendation is to remove the gearbox and send it in for NDT on the propshaft and also check the housing for cracks at the retaining bolt holes in the gearbox nose.  

Cheers