Ignition is locked

How do we unlock the ignition on our 2005 GMC Sierra 1500? Went running on errands and it was working just fine, then on to our next errand and the key wouldn’t turn! The steering wheel doesn’t lock though we have wiggled and turned it while trying to turn the key, we tapped the ignition opening (with a finger though we wanted to use a hammer!), and there doesn’t appear to be anything stuck in it. The gear selector (it is an automatic transmission) was in park when we turned it off but since we can’t even get the lights to come on, it is hard to tell if it has slipped or some such. In case it is helpful for diagnosis - it has ~50,000 miles on it, is 4WD, and is a V8.

Does the key slip in and out normally? Spray some WD-40 in the lock and see if it will free up. Try the other key. Call a Locksmith…