thanku for your concern,
well Amit it seems your baby is suffering most probably from tuberculosis
, as the skin test u did it came positive and the FNAC is also showing that possibility . there can be two possibility why the swelling is getting reduced with antibiotics 1)there can be secondary infection also which is getting response with that antibiotics 2)the antibiotics that your dr is giving can also be antitubecular like azithromycin
which treats normal throat infection as well as it is second line treatment for tuberculosis.
hence my advice will be to go for antitubercular treatment also.consult your pediatrician
i hope i have answered your query,