My question involves criminal law for the state of: New York

I was arrested with a DUI in NYS with nobody hurt and was sentenced on Oct 31st to three years probation. My first visit will be Wed Nov 5th and I dont know what to expect. I have never been arrested in 49 years and yea I have not had a single drink since june.

But now here is the kicker- I had smoked a joint with my bud about 2 1/2 weeks ago for the first time in months then I find out that I will get tested and Im not sure what I should do. Do I come clean or hope for the best and also what could happen????