If you see no clear path that he's taking to be sober NOW with good intentions then leave it along BUT by what you posted, he apparently doesn't see getting sober before nursing school as a priority so then I would report him. I have never been a "snitch" and disliked them most times but this is a big exception.
He has a serious drug problem (heroin and pills are NOT a joke, not even alcohol ) and the LAST thing I would hate to see is him get in (take someone's spot who worked their a$$ off to be there) and hide his addiction (which addicts learn to do well), then graduate and be my nurse. NO freaking way. SMH
Like I said, I am not promoting snitching by any means, I also don't think one should get in someone's way of making a better life for themselves whether they have a shady past or not.
Clearly, in this case he's so addicted he thinks he can "make it" as a nurse while popping/snorting and whatever else he does. Not cool.
Not fair for that one person who worked so hard to be there and now got wait listed and a complete hazard to all future patients.
PS. Even if he's drug tested an addict will research this and try to pass it.
EDIT: And yes, you need to BE SURE that he is back taking drugs like others said.