I'll definitely try that option. What if there is some object stuck in the keyhole? What's the best way to get it out?
hmm...
I don't know how that would happen, or it at least seems highly unlikely. I guess it's possible one of the tumblers broke and lodged in there, but I digress.
If you have something stuck in it you could try "flushing" the lock with (wd40, carb cleaner, pb blaster) or something of the sort. Then let it dry and dust it with graphite to re-lube. (I don't like this idea very much-but i've done it and as far as I can tell I didn't do damage. It very well could exacerbate your problem though since you are going to flush and lubricants you may have)
I dont think that would be your issue though. I think you just have a tumbler sticking. If I were you I would:
1. Puff that lock cylinder real good with graphite
2.Will the key go in now? If no, jiggle, fanagle, take in-out and try to work the graphite in.
3.Still won't go in? Stick the key as far in as it will go, and get you a hammer. VERY CAREFULLY give the key a few taps and try some more jiggling. Try more graphite, too.
4. Still no go? Head to the locksmith or pull the interior door panel off and swap the lock cylinder with the passenger side?