I have swollen lymph nodes on the side of my neck and behind ear. Some of them hurt. I have had them for a month. Is this serious?

Likely benign, but. The neck is a very common place for mild lymph node enlargements. We do about 5-6 lymph node biopsies a day-from the neck-and most of them are benign. However if rapid growth is noted, or if bigger than 3cm, or if other symptoms develop you need to have it checked. The most common cause of enlarged lymph nodes in the neck are a viral illness, a dental infection, skin infection and "other".