Can you do both? I have two jobs, my full time job and the other as a freelance translator. As bnockis mentioned, with these contract/freelance jobs you will probably have feast or famine; when it's good it's really great, but when it's low it's really hard to eek by on a low income that month. I use my freelance income as a bonus check that month and cannot rely on that cash flow on a regular basis.
I would be hesitant to give up your full time benefited nursing job, over a contract non-benefited job with a non guaranteed paycheck; unless you need to cut back on your work hours, which a contract/freelance job might just be the right fit.
If doing both jobs is an option, nursing full time and contract coding per diem/part time, then you might be in the best of both worlds. You get to keep your steady nursing job, but is still getting coding exposure and another income.
Best of luck!