screwed up a final exam

hi everybody. i’m new to this forum so tell me if I am doing anything wrong like posting in the wrong section or something along those lines thanks.

Anyway, i’m an undergrad student seeking to major in both finance and computer science. last semester i took multivariable calculus (cuz i just thought it would be a challenge and interesting). Though all was going decently, i had an 87 so i was on track to getting a b+ or a high b, I completely bombed the final as in failed it. this brought me down to a C. needless to say my parents and I were pretty disappointed. all that hard work over the semester and it just came crashing down.

Worst part is, i didn’t even have to take this class to fulfill my major requirements so i basically destroyed by gpa for nothing. I’m just worried since I’m applying for internships next semester and worried that grad schools will later see this grade on my transcript. I just don’t know what to do? Has this happened to anyone before? thanks.