Metatarsal fractures generally take around six to eight weeks to heal. It may take a bit longer if you have been putting weight on the foot. The non uniting fracture can be due to low blood supply, poor mineralization, presence of diabetes, presence of infection, poor alignment, or too much space between the fracture ends. This is treated by bone grafts, immobilization with plates and screws, or removal of scarred tissue from fractured ends. Basically all these processes need surgery. Consult an orthopedic surgeon. Take care!