I hit a tree root in my front yard and bent the lawnmower blade, instead of replacing I bent blade back and continued to mow yard I hit another root. Lawnmower engine is now very loud and engine shaking enough to unscrew nut that holds air filter in place.any suggestions? I tried to take off blade before this happen but was not sure how to do it. Is there a chance the blade is un balance now or have I done something worst?

Do not try to use this blade any further. It is totally junk and this point so you should buy a identical replacement. It is possible that you may have done some engine damage but that remains to be seen. Pull the spark plug wire and prop the mower on its side so you can reach the bolt in the center of the blade. Rotate the blade until it reaches the discharge and block it or wedge it with a 2 x 4 or similar block of wood. Lefty lossey should do it. If the engine still rattles after the new blade is installed you'll need a pro to see if its even worth repairing.
Good luck, Bob

Try A New Blade, A Bent Blade Can Cause Excessive Vibration. Remember That The Blade Is Rotating At 2800 To 3600 Rpms. If The Blade Is Not Bent, It Is The Crankshaft, And Probably Not Worth Repairing.