What Could Flat Brown Marking On Penis Shaft Suggest?

im and 14 years old and im worried about small brown markings on the shaft of my penis, they are about half a centmimeter in diameter or less, there are about 6 noticable markings, they have only started appearing in the past year or so. they are flat, they don't itch and i dont notice them unless i look at them so they dont cause me trouble but i would like to know why they are there and how to get rid of them. thank you