Changing graduation timeline, what do I do?

Hi everyone, I'd really appreciate any advice on this situation. 

I came into college with a good amount of credits that at the time would have possibly let me graduate early, but I wasn't sure how early or if it would be the case at all. Furthermore, these credits mostly covered my GenEd and elective courses. If I were to have graduated early, it would have been in 2024, though my "normal" graduating class is 2025. I did try to recruit for 2023 summer internships, but was often told by recruiters that since I was still in my second year, I should recruit for the 2025 application cycle (summer 2024). I also didn't have nearly enough knowledge to do well on interviews then.

I recently got an IB summer analyst offer for next year (more on the levfin/DCM side), which I'm very excited about, but it is part of the class of 2025 application cycle. I had to just commit to it, since mostly all of the 2024 FT positions were full before I started applying. My main worry is how I should go about telling HR that I now have clarity that its probably going to be my last year this upcoming fall, and will be graduating in spring 2024. I'm currently studying for level 1 of the CFA (Feb 2024 exam), and would probably spend a gap year studying for the level 2 exam, should I pass level 1. Am I screwed and will they rescind my offer? Thanks for taking the time to read this.