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, breast cancer, fungal infection, other cancers like lymphoma etc. If you had flu like symptoms initially then it could be due to infectious mononucleosis too. In your case in all probability it is the outer ear infection.