Even if you can apply for NOC 3011, it isn't in the priority list for Federal Skilled Worker class in Canada. Wait for the NOC 3152 to open up in July and then apply for that. Even if you are a head nurse in your country, you'd still start as a staff nurse in Canada without a license to practice.
I agree. If you look at the NOC that is on the skilled list 3011 isn't on it. If you can get a job offer or Arranged employment you should be able to apply for FSW2 which you can apply for even if the cap is closed. Otherwise wait until June/July and see if the RN is on the list. This gives you a bit of time to get everything together to send to Sydney NS