Are babies born with a broken collar bone in a significant amount of pain?

No: Based on experience with both infants and older children with fracture clavicles, the fracture per se does not appear particularly painful, unless the arm is manipulated. That is why stabilizing the arm is an important step in managing this condition, which generally heals itself within a few weeks.

Maybe,maybe not: I've had many that didn't seem to mind at all unless you touched the area & some that seemed to fuss a lot. Given that some newborns are like that with or without a fx clavicle, it's hard to say if it really matters to most. I've never had one tell me.