Go online to your state's BRN website and see if there is a link for verifying RN licensure. California does -and here is the link for new test takers in CA who need to know!! Results are posted as soon as two buisness days.
http://www2.dca.ca.gov/pls/wllpub/wllqryna$lcev2.startup?p_qte_code=RN&p_qte_pgm_code=7800