As you know, BMI is just a rough measurement, and there are many who dispute its validity for assessing optimal weight. If you're comfortable with how you look and feel, that's WAY more important than some silly chart. I also suspect you're well toned with good muscle definition, which likely explains why you're happy at your current weight.
For example, and to show the opposite side of the coin, I'm only an inch shorter than you and I weigh only 1 lb more. My BMI (according to the silly charts) is 26.1, only slightly above normal. If we think of BMI as the estimated percent of body fat, that would mean I'm about 26% body fat. No WAY! I can guarantee I'm a lot higher than that...the mirror tells me so. That just means I'm the opposite to you...I have little toning, not much muscle and too much fat (poor me
). That's in part due to my age (55) and in part due to many years of yo-yo dieting. So, I need to lose a lot more weight to look good. You apparently don't. So, kudos to you, for staying in such good shape!
Long story short, forget the charts and rely on the mirror. Oh...and forget what others say as well...it's how you feel that's important.