A positive Mantoux test
means that you have been exposed to the tuberculosis
bacilli in the past. It cannot tell for sure whether you are currently suffering from tuberculosis or not. Since your x-ray chest is normal and AFB stain misc is negative, it is not clear whether you are suffering from tuberculosis or not.
It is advisable to get a biopsy
of the lymph
node done as suggested by your doctor. This will help in arriving at a diagnosis so that appropriate treatment can be started.
Hope I have answered your query.