Hello, Lymph nodes are part of lymphatic system which carries fluid, nutrients, waste material between body tissue and blood stream. They are also part of body immune system active against disease by trapping various bacteria, viruses and killing them by lymphocytes. Cold & flu is a common condition in which lymph nodes can become swollen, other causes are injury, tumour, tuberculosis and lymphoma. You should consult a surgeon for further management and follow the instruction. You should undergo through several tests to rule out exact cause like- FNAC & Biopsy of lymph node, Total blood count, CT scan of head & neck region. Take care bye.