Don't ever talk to police. DON'T EVER TALK TO POLICE.
Call a lawyer and allow him to explain the mistake. There's just as much chance that the police could have used your explanation against you if they thought you were lying and you would be in jail right now, wrongfully convicted because you misremembered a small detail in your story.
DON'T EVER TALK TO POLICE, ESPECIALLY IF YOU HAVE BEEN EXPLICITLY CHARGED WITH A CRIME.