If you are getting a refund there is no penalty for filing late, so you have nothing to worry about.
If you have a payment due, you could be charged penalties for late filing and late payment. But the penalties for being a day late are not going to be very much. The IRS might not even bother to collect a small penalty. In any case, there's nothing you can do about it now, so you just have to wait to see what happens.
