Medication Error

I got my Lvn about 7 months ago. Recently at my current job (SNF) a medication error occurred. I was assigned a station as the CN for a very hectic and overwhelming station. Census is about 30 patients. So, I come in for the day and unexpectedly had a new grad trainee on top of two students. Everything was fine until the end of the shift. We were already sending out another patient and in order to get everything done including the med pass in a timely hour.. I made the mistake of allowing the new hire to pass meds while I finish all the paperwork and charting. Unfortunately, she was still signed under my MAR when passing medications. She needed assistance and I went over to help her. Together we pulled a patients pain medication (which was 4 hours late) and I signed the narcotic out. I let her walk away with the medication and continue to pass meds. About 40mins later a patient has to be sent out and is stating that he does not know what she gave him. I confirm with her that she gave him his pain medication and she said yes. But I know this is a big error. I really don't want to lose my license from a mistake. I am still learning, was very overwhelmed and don't think I should be training anyone. I'm not sure what to do. 

?Not a patient. The patient we signed out the narcotic for. Sorry