You did not say what is wrong with you, but I understand your wanting to follow God's will for your life. I had to give up teaching, because I was so disabled by Rheumatoid Arthritis. Then, I went to seminary to become a pastor or chaplain and even had a job offer. But my meds failed, and that was the end of that! But, for me, getting a seminary education is something I use every day!
Not so with nursing! My thought is that there is sometimes heavy lifting involved with nursing, although an RA is doing more administrative things. What is that would keep you from performing your duties, if you completed your Bachelor of Nursing? (This is a rhetorical question for you to answer, you don't need to answer it in this thread!)
Being in health care is very demanding. There are long hours, and it can make a body that is already struggling even worse. I have a son-in-law and a daughter-in-law who are doctors and the work, and on call they go through is incredible. And long, long hours! But they are both extremely healthy, with supportive spouses.
So you are going to have to reason this out, with the brains God gave you. Sometimes he won't light up the sky with an answer, but just tell you that your body is speaking for him. Or not! That is for you to figure out!