Don't compete your junior year. You shouldn't even try. Puberty is a bitch. You may think it won't get you, but it will sneak up behind you and rob you of everything you ever loved about running. So don't fight it. Take a year off and run on your own just because you want to. Because you enjoy it. And understand just how precious that is, the enjoyment of it. And then come back your senior year and kick ass again. Don't worry, college coaches will still want you. You've already proven that you're talented.
If you don't take the time to let yourself grow into your body, puberty will leave your broken. It will steal your confidence and your fearlessness. You know how good it feels to beat all those juniors and seniors right now? Well, soon that will be you getting beat by the newest freshman phenom on the block. Then you'll start looking back instead of forward, just praying not to get passed. You'll develop eating issues which you will probably be able to somewhat manage in high school, but will get out of control and consume you in college. It will be a year of tears, heartbreak and frustration. Then you'll spend your senior year just trying to rebuild yourself and erase the memories of last year's failures.
So just save yourself the headache and spend a year running for the love of it. Puberty can drain you of all your desire and motivation and you'll forget why you're even doing it anymore. When you get to college you'll realize this is the one injury you can't come back from.