I omitted an expunged juvenile felony from my enlistment?

Long story short, when I was 15 I was convicted for giving a controlled substance (a perscription) to someone in school. It was expunged when I turned 18. A friend of mine in the military called the FBI to check for a record in the NCIC, nothing came back. Now I'm enlisting in the military and have omitted this felony, and plan on taking a job that doesn't require security clearance. I'm looking for advice from someone who actually knows something about this. It isn't waiverable and I see no other way to enlist. Question is, if I keep my head down and don't bring it up, will I be ok?