Your collar's transforming you. Mature.
It's so heavy, so thick, and so large that it's more a belt than a collar. The studded strap is tall enough to reach from the bottom of your ear to your shoulder, and long enough to hang down to your chest. If you could, you'd be able to slip the collar off easily.
But you can't. It's already started.
It's indistinguishable from your own embarrassment at first. Heat on your cheeks, sweat that makes every motion come with a chill, and your stomach curling up into a ball. Your heart beats faster and your breath grows shallow. You can't tell what's your own anxiety and what's the change. You can't wait any longer. You don't want this, but drawing this out forever is even worse.
Your joints lock first. You fall to the ground on your knees, your toes curled back against the ground and your fingers bending inward. You hold onto the collar itself for support and try to straighten your fingers, but the tendons along your arm sear with pain. With a cry of pain, you drop your hand to the floor.
The heat across your body rises. You break out in a fresh sweat, but your chest is dry. Your chest is prickling. You fight with the collar for an easy way to scratch that bristling feeling. It's like a hair brush against your bare skin. You shove your curled fingers under the collar and start scratching, but it barely helps. You're still sweating.
Then a pulse goes through you. It starts between your shoulders and rolls down over your spine, jumping from bone to bone, to the tips of your fingers and toes. The first creak of bone makes you shudder. As your spine is pulled from both ends, it stretches muscle and pulls skin tight. But at the same time, it's a small release. Your joints crack as they settle into their new shape. You curl your back. As each joint pops, the pain of growing bone diffuses into your skin.