You were delegated to improperly........that's the fault of the RN who should have done this task herself. You also performed a task that you aren't licensed to perform......that was YOUR fault, and if you are as smart as I think you are, you won't do it again.
I know it can be difficult to stay within a CNA/tech's scope of practice when you're a nursing student; during my own nursing program, I worked as a CNA and could only watch while the nurses performed procedures I'd been trained to do, but was not licensed to do. It was especially difficult to keep my hands out of a situation like that of the patient who needed an NG tube insertion; the RN I was working with had never put one down a live patient, while as a student, I'd done two of them! But as the aide, I could no more perform this procedure legally than fly to the moon, so I ended up sort of coaching the nurse through it........and between the two of us, it got done.
If this is the worst mistake you ever make in your career, you'll be very fortunate. Everyone
screws up at one time or another, and any nurse who says s/he has never made a med error, forgotten something, or hung the wrong IV solution is lying out their kazoo. Just remember, you don't want to lose your license before you ever get it by taking on a task or skill you are not legally permitted by your state to perform......and next time a RN or LPN asks you to do something like this, say NO!!
Best of luck to you.