sudden problem w ignition key
 

After cold overnight at my cabin deep in north woods this week, my ignition key on my primary key group wouldn't turn at all. Seemed locked in off position. Jiggling the steering wheel didn't help. Fortunately had an extra key on separate ring and worked fine. Key turned, started up, turned off. Tried first key again and this time okay.
I had been in 4L Selectrac and had backed in between trees, cramping wheel hard before shutdown if that's a clue.
These two keys work do not work on passenger-side door but are/were fine on driver's door, back hatch, glove box, and of course ignition. Is that another clue or just a forget-it item?
Problem repeated itself a day later in parking lot. Switched keys fine, followed by no problem with first key again.
I do need two working keys, so any ideas? Thank you, one and all on behalf of my 2000 Cherokee Sport XJ...