Your key could be worn. Try moving your steering wheel while turning the ignition. If the locked steering is in a bind the key will not turn over.
So it would seem. If the ignition is in the column it may also be jammed by the steering wheel lock. Try turning the steering wheel and holding it while turning the ignition key.
Step on brake first. Turn steering wheel slightly to remove tension on key.
You could try turning your steering wheel both directions to release pressure then turn.
make sure the steering wheel isn't locked
There may be something jammed inside your ignition. If this is not the problem then you will need to have a new ignition installed.
hmm im just guessing but try turning the steering wheel either direction while trying to turn the key in the ignition. you may have to try turning the wheel both ways.
try wiggling the steering wheel it has a lock on it
try turning the steering wheel to the left or right and holding it there while turning the key
Older Chevy's have a steering lock when the key isn't in the ignition.
Try turning steering wheel slightly while you do it.
you wont be able to turn the steering wheel so easily if you dont fix it you wont be able to turn it at all