Hello There are certain things that you need to add in you question Is there any fever, weight loss, fatigue or night sweats? As because these presence or absence of these can alter your diagnosis completely. Swollen posterior cervical nodes may occur from even dandruff. So kindly do not straightaway worry about malignancy. Tenderness in lymph node usually occurs in infection . And persistent swelling without change in size or increase in number of lymph nodes usually would indicate a persistent infection. You need a re-evaluation and a pan endoscopy for excluding other diseases. Excisional biospy is not advisable without another trial of broad spectrum antibiotics or a complete evaluation. Hope this helps you.