Honesty is and shall remain the best policy in any sphere of life. Acknowledging a mistake, however small, is all the more appreciated for putting things in perspective, be it through a small correction or a big, detailed explanation. Just write, apologize, and request a correction to be made to the concerned.
I can recount numerous examples in my professional life for that, but that is not required here. Mark my words - an oral pat on the back by a very senior person adds to your stature more than a paper enhancement of your emoluments.
Warm regards,
Shivkumar R.