Askold, you might not want to wait too long. Especially in winter. Any little bit of moisture gets in and refreezes and expands, you'll go from a crack to shattered overnight. At least that's what the windshield guy told me last winter.
@ Ghoti, have you thought about making a spare car key? One to keep in your wallet. Not only is it useful for situations like yours, but it dabbed me lots of money over the years for those rate occasions when I'd lock my keys in my car. IDK, I hate like hell seeing bad things happen to good people for stupid reasons. That was a bad thing for a stupid reason and you're one of the good people.