Looks like someone needs a history lesson!

Justin Bieber appeared on The Late Show with David Letterman last night, and let's just say things got awkward really quickly...

The talk show host began chastising the pop star about his various tattoos, and when he reached over to try and grab one of the fresh tats to get a closer look, the "Boyfriend" singer cried out in pain and lashed out, quipping, "Grandpas." Yikes!

Letterman cautioned the teen sensation not to cover his body in ink, for fear he might start looking like the Sistine Chapel, and The Biebs made himself sound a little ignorant without knowing it by saying, "I'm not going for the Sixteenth Chapel." The gap toothed funny man didn't skip a beat, exclaiming, "Canadian high school!"

Oh man JB, it looks like you might want to dedicate less time to body art and more time to sessions with your tutor!