Is Getting A “b” Grade Bad For A Major Related Course?

I just finished taking winter intersession in my community college for Macroeconomics 101, and I got a B in the course. This was in part due to me slacking off a little in a 6 week accelerated learning course, and because the total points attainable was 200, there was little room to slack. I was actually a few points from an A. I regret slacking. My major is either Business or Economics. I enjoyed the course and the professor. I felt like I learned a lot about the economy in 6 weeks. But would you say getting a B in a major-related course is bad? I plan on transferring to a top four-year university and going to graduate school. Please share from your personal experience. My current GPA is 3.53, and Spring starts next Tuesday for me. So I have time to raise my GPA to a 3.7+.