ssandy, yes you can still apply to immigrate to canada even though you are out of status in U.S.
If you have a valid visa for at least a year here in us, you can file to one of the offices here in U.S.
If you entered here in US as a tourist and you were granted less than a year, you can definitely apply as FSW to canada to your country of origin. RN is listed on one of the 38 occupational list that are highly in demand in canada and will be fast tracked provided you meet the rest of the requirements.
Check CIC website, there you will see the needed requirements.
I am a nurse myself, out of status here in US, applied in CIC-MANILA and just waiting for my medical request.
Start your application ASAP, nurses are really in high demand in CANADA and everywhere else.