I never understand why teenage boys are told constantly from every source that size is not important by men and women with far more experience than they could hope to have and they always listen to the one person who says penis size will somehow measure their ability to give pleasure to someone else.

So you asked a question. The bulk of your sexual development happens during the 4 years following the first signs of puberty, acne, body hair etc. This is usually somewhere in the range of 13-17 for most boys. This means after 17 it is very unusual that you will see the kinds of growth spurts that cause significant differences in penis size. Your body will adjust as you mature into adulthood you could see another quarter of an inch of length in the following 10 years, perhaps a slight change in girth.

Most importantly, you're 16. You could gain 8 inches of length in three months. There's no way of predicting how you'll develop until you're a fully grown adult and there's no point in worrying about it until you've stopped growing. Stop putting a lot of brainpower behind your penis. You'll discover that it makes you a much better lover.