I agree. If the grade is already in, don’t worry about it, and just move forward. If you haven’t taken the final yet, get off of CC and get access to someone who can help you, and just prep like mad, to do your absolute best on the final exam.
As already said, this one B will not kill your applications. Your safety and match schools won’t reject you because of it, and it wouldn’t stop your reach/dream schools from accepting you, if they want you for other reasons. And if what you want is Comp Sci, know that people who graduate with a degree in this from anywhere are getting great jobs - after that first job, it’s only about whether you can do the job, no one really cares that much where you went.
If it’s done, forget about it and move on. If not, put your all into prepping for the final.