Don't worry about it, BMI is a load of tosh, and is only a very rough guide... international rugby players (backs, not forwards) often fall into the obese category.
I was 'borderline obese' according to BMI - at a time when I cycled everyday, went to the gym 4-5 times a week and ran circa 100 miles a week (and completed marathons in a respectable time). The scale does not take into account the differing weight of fat and muscle etc.
As long as you are fit and healthy and not too overweight, you will be fine.