Why did you become a nurse? Why don’t want to continue being a nurse? Those are your answers — unless you no longer want to be a nurse that is.
But you don’t have to say anything. No need to embellish or lie. If you’re asked directly, do you like your job, then just say yes, you like your job. You have no incentive or reason to say anything more than that. If someone prods you for more info, you should ask them why they want to know.
If you feel pressured into saying more, then go back to why you wanted to be a nurse. Keep it simple. Don’t give more than what you’re asked. Stick to facts and leave your emotions out of it.