Providing the fracture had completely healed prior to you running again, it would unusual for it to have re-fractured the same area since calcification makes the bone stronger at the site of injury than before. However, if it had not completely healed, then it is possible to re-fracture the site.
I have had a femoral neck stress fracture and from my experience, there were some slight pains noticed after recommencing running. I would be particularly careful if this dull pain is persisting as this may well be re-injury. Did you get an MRI to ensure the fracture had healed completely prior to returning to training? Femoral neck stress fractures are a very serious stress fracture to have and according to the medical advice I received from the orthopaedic surgeon, if it has not completely healed prior to returning to sport, it is likely to re-fracture and potentially require surgery to stabilise the femoral neck.
Also, femoral neck stress fractures are not all that uncommon in female distance runners, particularly those with amenorrhea (female athlete triad).
It best to be overly cautious with this. And if you are female, go get a bone density scan/see an endocrinologist as this is location of fracture is a red flag for low bone density.