Dear friend, welcome and thanks for entrusting your query here at HCM!
I am Dr. Prasad Akole (Critical Care Expert- http://bit.ly/Dr-Prasad-Akole) and am glad to address to your query here.
Hard lymph nodes below the jaw which are not going even with a month of antibiotics are suspicious.
Usually they enlarge in response to infection, but disappear after an appropriate antibiotic.
Persistence should be evaluated by a surgeon for possible Tuberculosis
A lymph node biopsy
may be needed if the doctor finds appropriate on clinical examination.
I hope you are fully satisfied with the guidance I gave.
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Thank you and Good luck!