Willie Nelson's Son -- Sorry Officer, No Drugs Here!

Police in Ohio got a tip that someone on Willie Nelson's son's tour bus was carrying drugs yesterday ... but here's the shocking part -- IT WASN'T WILLIE NELSON'S SON!!!

Turns out, Willie's 22-year-old kid Lukas Nelson is also a musician -- and yesterday his band was stopped in Ohio when local police got a tip that someone on the bus was in possession of some weed.

Centerville Police Department Officer Matt Dunn tells TMZ ... a drug sniffing dog was sent to the scene and tipped off police to a suspect ... a member of Lukas' band.

Cops say the band member had a small amount of weed in his possession and he was arrested for misdemeanor possession of marijuana.

As for Lukas -- dude was squeaky clean ... and after cops hauled away the band member, Lukas and his posse were sent on their way.