...It's not that big of a crime, first of all. Secondly, your character really didn't mean to do it that way. The door was locked when it shouldn't have been, and you got curious as to why. In the future though, just note that shops don't always open exactly when they're supposed to. Just like NPCs aren't always to be found where they're supposed to be found.
Do some sort of atonement (as Averae says). Go to jail, be shamed for awhile. But then get back on your feet at some point and keep up the good works.
My paladin has made a couple mistakes. Once she went to talk to somebody, for instance, but a horse was standing next to her. So when I pressed the Activate button, she (of course) wound up getting on the horse! :facepalm: The NPC attacked her, and Dyan immediately just started yielding in battle (instead of attacking back or running away). Eventually, the NPC (it was a farmer) finally yielded, everything was cool. :clap: