First of all, correct it on any more resumes that you send out. Having false information on your application, including your resume, is the very best way of making sure you don't get hired/get fired when it is caught.
Frankly, neither option is very good, but correcting it in the interview is the better of the two. That way you only look sloppy. If you leave it alone hoping it won't get discovered (and if they do even the most cursory reference check it WILL get discovered) it's a sure thing that your application will immediately go into the "not interested" pile.
If by some chance it slips through and you are hired, but your employer finds out later that the information is incorrect (and that is FAR easier than you might think even after hire) you will be fired.