Usually a cracking or popping sensation is due to arthritis or due to a ligament tear. It can also be a healing stress fracture. If it is osetonecrosis, then you may need bone stimulation or surgery.
As it is, you will have to use a plaster cast or crutches or CAM boots or splints to avoid putting pressure on the foot. Once there the bone has healed, physiotherapy will be started.
You may need a CT scan to differentiate between osteonecrosis or stress fracture. Treatment will depend on diagnosis. Please discuss with your doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.