If one of the rules which nurses must follow in your state is to not commit crimes (i.e. you can lose your license or be suspended acts), then you can't use even medical marijuana, since regardless of its legality under OK law, marijuana is stiill illegal under federal law (it is a CDS, or controlled dangerous substance, under federal law), and so using it is still a criminal act even if legal under your state's law (since federal law applies everywhere). So depending on your state's licensing standards, this could be an issue.Also, even if your state's licensing standards are not a problem, note that  any institution (e.g. hospital) which gets any federal funding in any way could not employ someone using a drug illegal under federal law, so you could face some restrictions on employment.