Have a question concerning my penis?

Im 17 years old bout to be 18 in a month. Ok so I went into the bathroom and i noticed something odd about penis. I noticed near the base and to the middle it looked large but the top half is small? Is it my penis growing in girth? I squeezed around to notice if there is any pain but nothing? Soo it seemed kinda of a scary ordeal! Have any thoughts is to wat it is? Thanx!