Prescription fraud how to handle?

My 20 year old son had a legitimate prescription for a drug dated the 15th he changed the date to the 13th and filled it. he did not realize how serious this would be vif he was caught! I am wondering what are the odds . he is very sorry it was a foolish thing to do and he is scared will be caught. at this point, would it do any good to approach the pharmacist fess up and beg leniency or just ride it out hope for the best?