I agree, ask your SU for advice. They may be able to send a rep with you who can help you or talk you through the university procedures.
Show total contrition and take responsibility. Show remorse, and explain how it will not happen again (e.g. you will allow more time for assignments so you are not rushing them). Explain how much the course means to you, and if you can draw on examples that will show you can be a good nurse despite this mistake.
They haven't said you will definitely be expelled, just that it is a possibility. The university won't want to kick you out, just impress on you that this is a very serious offense.
I do think if they give you another chance, it will really be your final one- and so you must make sure it does not happen again.