How much will my freshman grades matter?

Hi, I am ninth grade (freshman) in California from a school with 600 kids in my class. I took AP Calculus BC from an online program run by Stanford and got an A first semester, and a B+ second semester. In my normal school, I have all A’s except 1 B in English both semesters.
This year I also qualified for AIME, participated in school theater, played jv tennis, and volunteered at a deaf school where I tutored Math (I learned ASL for this).
I just wanted to know how much my B+ in my second semester of Calculus will hurt me? Will colleges like MIT which are STEM-oriented think I took this course to early and utterly failed (what happened is that I had an A until I bombed my final and ended up with a B+)?

Why did you take AP calculus freshman year?

Because I was already ahead and had A’s in AP Calc AB in 8th grade and got a 5 on the exam so I thought I was ready.

Kid, you’re fine. Don’t worry about that. Most people (myself included) are perfectly happy with a B+ in AP Calc BC, especially if I were to take it as a freshman. If anything, colleges would be impressed by that, and a B+ is far from an utter failure.

As long as you did well on the exam and you get a ~800 on SAT math you should be good.
What math are you taking next year?

Multivariable and AP Physics C

Honestly, you are so fine if you are taking those courses as a sophomore. Please don’t worry, it is slightly annoying (but that’s ok) to see people worried about a problem that isn’t actually a problem.