hit sewer lid,engine stopped, wont start

There are safety switches on all lawn tractors, and given such a jolt as you say hitting a sewer lid, I would suspect connector was knocked loose or is not connected, this would prevent mower from starting, so look for wire going to switch on deck area and check for good connection. Switch may be located attached to your blade engagement handle, so it depends on model which is not mentioned.

Can you turn blade manually with your hand, this would eliminate possible damage to engine if blade was damaged which could lead to broken motor. Does it try to start, as in turn over but not start? You need to be more specific, it is rare that an engine crankshaft would break unless blade is directly connected to engine, not common these days, most have belt drives.

muffmueller we will need to get more info from you to answer this. we need to know the make, model and engine of your mower. Right now you will most likely have to replace the shear pin. your timing etc. will be off to prevent any further damage when hitting stationary object. Until we know what we are dealing with, there is no way to give you any valid answer.

Aren't sewer lids in the street? Were you illegally driving a riding mower down the street?