It varies... Most stress fractures of the foot can be treated with relative rest and immobilization (boot walker or cast). It is important to determine causes, and correct these in order to prevent a recurrence. Overtraining, poor footwear, inadequate calcium/vit. D in the diet and poor walking/running mechanics can be causative factors. Those involving the 5th metatarsal & navicular need special attention.
Rest. Stress fractures usually are not displaced and heal with reduced activity levels and good old fashion time.