I have been practicing Reiki professionally for 26 years and teaching for 22, and I encourage you to develop yourself as a Reiki practitioner by giving yourself a full hands-on Reiki self-treatment everyday without fail. Nurses understandably often approach Reiki as a health care intervention, but it is actually a spiritual healing practice, and the best way to develop a deep understanding of what is possible is by experiencing the benefits for yourself, especially if you are thinking of teaching some day.
It is certainly possible to have a Reiki business, especially today, but it requires the development of three very different skill sets, those of a business person, a Reiki practitioner, and a teacher. You will find much overlap from your nursing experience, but not all of it will translate.
For the past year, I have been training nurses in the peri-operative department of a hospital in NYC, and the focus is on self-care practice first. Nursing is a profession with a serious burnout problem -- I'm sure I don't have to tell you that! :-)
From the foundation of self-care (which my students often describe as life-changing), nurses begin offering patients moments of Reiki touch, or a brief modified treatment, and quickly see the results. So if you continue your nursing job (which seems like a good idea for now), you might start by integrating Reiki moments into routine care, and let your experience deepen while your patients teach you.
Here are some resources you might be interested in. You'll find a free recording of a Reiki presentation I gave at a medical conference at Reiki In Medicine.org, and Reiki research papers, including a study we did at Yale published in the Journal of the American College of Cardiology, at the Medical Papers page.