What are the most common symptoms of broken bone?

Pain/bruise/swelling: Bones have most of their living structure on the outside surface, like bark on a tree. Bone bruises can produce significant pain, but breaks will add some blood pooling (bruising) & swelling to the mix. The more dramatic the fracture the more likely a visable deformity & rarely bone parts will stick out thru the skin.

Pain: Unless you have some congenital disorder that doesn't allow you to feel pain then pain would be the most common symptom of a fracture.