Hi, and thanks for your query on eHealth forum!
A tooth infection should not cause a lymph node to swell in your collar bone area. Yes, supraclavicular lymphadenopathy (lymphnode in area between collar bone and jaw) is worrisome. Especially the ones larger than 1cm in diameter should be investigated thoroughly for cancers and granulomatous diseases. The right supraclavicular area receives drainage from the organs in chest, whereas the left supraclavicular lymph nodes drain the abdomen. The supraclavicular lymph nodes also receive lymphatic drainage from the breasts. Hence the malignancies of these regions are possible. Tuberculosis, sarcoidosis, histoplasmosis, cat scratch disease and cryptococcosis are the other possibilities.
I understand the anxiety and since you have a history of tuberculosis, this should be ruled out first. A fine needle aspiration cytology should be done. Since it has probably recurred, it would be best to excise the lymph node, send it to biopsy and re-start anti-tubercular treatment after testing for sensitivity to anti-tubercular drugs. Since a confirmed diagnosis cannot be given on net please consult your doctor to find whether TB has recurred, and best mode of treatment. Hope this helps. Take care!