I disagree with Talldoctor. Nothing wrong with getting involved early, as long as you try to keep some perspective. And I assume you'll be in college soon anyway.
To your point though, I just got into med school after going through undergrad + a masters (6yrs), and I can honestly tell you I don't remember a single thing about high school. I can't even name fifteen of my high school classmates. Your whole life is going to change in the next few years. Whether you come out the other side still wanting to be a doctor, just keep in mind that now is not the time to make final decisions about your future career. The person that makes that decision in 4yrs is going to be a completely different you.
And if you're worried about screwing up a splint after your first try, don't. I think younger people have this notion that the only ones that get into med school are those who are born having the innate ability to intubate a patient or throw a stitch. Everyone fumbles everything in the beginning. If it's an important skill and you don't get it immediately, practice. One thing you'll notice in med school is wannabe surgeons walking around practicing their surgical knots with the drawstrings of their scrub bottoms for HOURS. It doesn't take much conscious effort, but even for something that small, they do it everywhere they go.
For now, keep exploring medicine if you really want it. Join interest groups in college and shadow a ton. Do well in your classes so if you do decide you want to go to med school, you've put yourself in a solid position to do so. And if you get towards the middle/end of college and decide you don't love it, try something else.