Riding lawn mower is making extremely loud clanking sound?
I've pulled the blade off and restarted it again but it still makes the sound. The sound is coming from inside the engine and it happend right after I ran over a few sticks..did i bend the shaft? Is that easy to repair?

If there's nothing visible from the outside, any stick fiber/pieces jambed around the shaft or other moving part(s), you'll have to tear it down and go inside. If it is the shaft, I don't think you can straighten it out.
If you have a schematic/break down of the engine and you feel handy about making your own repairs, you'll save in the labor department.
if the shaft is bent No
blade is hitting the cover
I don't think a few sticks would bend the shaft unless they were big ones. if you still have the clanking after you removed the blade sure sound it is time for an overhaul of the engine or a new one
I would pull the cowling off the engine and the nut from the flywheel and see if the key is sheared. It could be the flywheel hitting something. You don't usually bend the crankshaft on a riding mower because it it coupled to the engine with a belt.