There is the “120 day rule” for brand new nurse aides. This allows a person to work as a nurse aide for 120 days. At the end of the 120 days the person must be active on the registry.
CFR 42 483.75 – 483.158 - Federal statutes governing nurse aides
§ 483.75 (5) Registry verification.
Before allowing an individual to serve as a nurse aide, a facility must receive registry verification that the individual has met competency evaluation requirements unless:
(i) The individual is a full-time employee in a training and competency evaluation program approved by the State; or
(ii) The individual can prove that he or she has recently successfully completed a training and competency evaluation program or competency evaluation program approved by the State and has not yet been included in the registry. Facilities must follow up to ensure that such an individual actually becomes registered.
NAC Title 172, Chapter 108 - Approval of Training Programs and Qualifications for Nursing Assistants in Nursing Homes
In order for an individual to be eligible for employment as a nursing assistant in a nursing home, the individual:
4. Must successfully complete, within 120 days of employment, a nursing assistant training course approved by the Nebraska Department of Health and Human Services.
I am confident this is correct but it is not legal advice and you should contact the Nebraska Nurse Aide Registry at 402-471-4969 to avoid any potential problems.