When lymph nodes enlarge in response to an infection or some other immune system trigger, they may become painful or tender with or without fever. Lymph nodes that are painful or tender are usually associated with an infection, but with many infections the lymph nodes do not cause discomfort.
Let's see if you have any other symptoms that suggest the cause of the swollen lymph nodes.
In addition to swollen lymph nodes in the neck, do you have a sore throat or yellow-white patches on your tonsils?