I remember when my younger daughter got her first B. It was a B+ in a history class in high school. I told her it was fine. We stopped to get ice cream on the way home from school. I was in fact very glad when she got it. It made the point that she did not need to be perfect. She still got accepted to very good universities that were a good fit for her and affordable for us. She did very well in university, and is currently just finishing the first year of a very good PhD program. She learned from this B. She learned to be a better student.
Recently (this all occurred about 8 or 9 years ago) she told me that she remembers this and remembers that we stopped to get ice cream.
You do not need to be perfect either.
Missing time in the middle of a school year is tough. This makes it hard to do well in school, and you are doing very well if this only resulted in one B.
When you get to applying to universities, your freshman year of high school will be a lot less important compared to other years of high school. Some universities do not even care about freshman year as long as you pass your classes.
Are you in California? I am pretty sure that the various Universities of California, including UC Berkeley and UC Irvine, are included in the list of schools that do not care about your freshman year.
You might want to spend a bit of time over the summer to make sure that you are caught up in math and ready for next year’s classes.
Otherwise I would not worry about it.