Definitely sounds like you have bigger issues - either the keyway in the crank is damaged, or the gear itself is damaged. If the crank is in good shape, and the key fits snugly in the slot, you should be able to get away with replacing the timing gear.
If the crank keyway is loose, start pricing out a new crank or a new engine.....

If you try and put it back together the way it is, you're going to be sitting on a time bomb...