Diabetes can delay or impair fracture healing so excellent control with insulin (in your case) is important.
Also, with the nature of this fracture - base of the metatarsal fracture - a fair number of patients show poor healing (non union)...independent of co morbidities (e.g. diabetes). Therefore surgical fixation of the fracture is sometimes needed.
Post operatively, it will be important to not only assess fracture healing and bony alignment but to monitor incision site healing.
Also, you will need to have a pre operative evaluation to assess your heart and lung condition prior to have surgery.
All in all, not surprising that the bone is not healing after 8 weeks but there are often performed surgical procedures to fix the bone.
Tom Plamondon PA-C, PT