Justin Bieber -- Here's Why the Cops Stopped Me

Justin Bieber was super cool Friday night when he breezed into The Nice Guy in WeHo, telling our photog why he REALLY got nailed by cops.

In case you didn't see ... the Biebs was leaving The Grove Friday afternoon when he peeled out, and eyewitnesses said the cops ticketed him for reckless driving.

Not so ... Biebs concedes he broke the law, but for a different driving move.

Corey Gamble is also in the video playing Justin's hype man, as Bieber gives our photog the lowdown on his latest tat.