Neck lymph nodes can be the result of tonsillitis, pharyngitis (infection of upper throat), infection in mouth, caries in tooth, internal ear infection, outer ear infection, eczema, dermatitis, dandruff, fungal infection, other cancers like lymphoma etc. If you had flu like symptoms initially then it could be due to infectious mononucleosis too.
Other lumps in neck could be a lipoma, neurofibroma (collection of nerve and fibrous tissue), a ganglion or a cyst. An ultrasound would be diagnostic. Please discuss this with your doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.