I am bewildered by the fact that you were started on anti koch's treatment. The investigation of choice for foot pain is a local x ray
to look for any bony lesion followed by a vascular doppler to study the blood supply of that part. these are the commonest causes for foot pain. Only if there is any positive lesion picked up on x ray then further investigation is required. Montoux test in Indian population does not carry any weght as everyone of us is administered BCG
at birth. So the reading of the test is doubtful.I would suggest you to stop anti koch's treatment and seek a surgical opinion.