He's had a metal old mailbox door fall on his collarbone and i'm not sure if it could be fractured broken or just really proves what would the symptoms be if it were broken or get fractured or even bruised?

Take your 2 yo son to a pediatrician for an exam. Is is difficult at age 2 to precisely judge the degree of pain or injury. Children will favor the affected area, and it will be difficult to assess the cause.

The symptoms could be the same. Probably tenderness and decreased use of the arm. A x-ray would be helpful. Follow with your PCP for further treatment.