For the BMI, the scales are all you need... But BMI is universal, whilst body types are not. Big bones and muscles mean you can be heavier whilst still being healthy, and vice versa for the contrary. A doctor should be able to give you a more advanced BMI scale adapted to your body type. From that, just stay in the "healthy weight" area.
Sometimes, being a little (A LITTLE) underweight is okay if you base yourself on an universal scale, but if you get a customized scale, you should never leave the healthy weight area.
My opinion would be to aim for the lower area of the healthy area without leaving it, since it's easy to accidentally gain weight and go into the overweight area, but the contrary is much more rare.
Generally, silhouette-wise, the general opinion is to try to get as close as possible to an hourglass shape (hips > waist). So the ideal is to have sufficient fat on your hips. So again, not too thin.
As for your universal BMI right now, I think it's quite all right. You COULD lose some weight if you think it'd make you feel better, but you're really okay. But I don't know how your bones and muscles are.
I hope it helped.