Growing pains maybe? (Which I recently learned is a real thing, I don't remember experiencing them at all)
So you're no longer going to be the smol bean carried around by everyone
Well, I thought I had growing pains in my legs, turns out it was just a hernia. Maybe you'd want to get that checked out if the pain persists or is subject to alterations in elevation, humidity, air pressure... The works. Most likely you're going from a bean to a bean sprout
I don't know if I had any kind of growing pains at fifteen, the only leg pain I went through at that age was a muscle tear after I tried to squat more weight than I could handle.
So you're no longer going to be the smol bean carried around by everyone