when a bone breaks it creates pressure and tension in the tissues around the bones, and they are connected to nerves and tendons, so, it hurts like crazy.

What makes you think it would be painless in the first place?

There are two portions to the nervous system. The first is the CNS (central nervous system), that consists of the brain and the spinal cord. The CNS attaches to the PNS (peripheral nervous system), and impulses from the PNS get relayed to the brain via the CNS. A bone is called ossified tissue, because through a calcification of cartilege, and some other processes, the bone material hardens. PNS nerve tissue grows out from the central parts of the larger PNS strands and branches into the bone tissue. There are plenty of nerves in bone tissue because of that. In the case of the spine, both the CNS and the PNS have nerves that run through those bones. When bones break, the nerves will be severed to the degree that the bone tissue is fissured. In the case of the PNS, unlike the CNS, nerve fibers will grow back -- albeit Very Slowly. If there is a break in the CNS, good luck at having any regrowth. Your body is a sensory organ. There are nerves, lymph ducts, and circulatory systems galore. It's a marvelous place. Until you break a bone I guess! I hope this answered your question. You can also look stuff up on wikipedia for a more complete answer if you like.

There are nerves inside the bone as well.

Every bone in the body is covered with a kind of 'skin' called periosteum, which has many nerve endings. It's injury to the periosteum that's responsible for most of the pain of fractures.