Small Engines (Lawn Mowers, etc.): Push Mower Vibration, spark plug, crankshaft

Question
I think I may have damaged my mower the last time I used it. I accidently let the mower down too far on a small stump and of course the mower stopped running.

After I got it started again the mower vibrates so badly I can hardly hold on to it after I start it. I am not sure what to do. I did not notice anything bent, but honestly I only looked at the blade with my naked eye. What do you think?

Answer
 Hello Sal:

 Remove the Spark Plug. Tilt Mower Away from Spark Plug and Remove the Blade. Replace the Blade Bolt just a Few Turns. Turn the Mower and Watch the Blade Bolt. Does it Wobble. If Yes, then the Crankshaft is Bent and is Causing the Vibration. If No, then the Blade is Bent and is Causing the Vibration. I would Suggest too that you Inspect the Flywheel Key for Damage. Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John