My six-year-old son has from one year old many visible small lymph nodes in his neck that appear because he is very thin. one remains larger for many years on the left side of the tonsil when he turns up head. blood tests ok ent ok. should i worry?

Not particularly: Lymph nodes in the neck & back of the head are often more noticeable because they are not buried within fat or deep tissues. They are generally pea sized at rest & enlarge when working. Skin irritation, URI's, throat infections, etc commonly trigger transient enlargement for weeks at a time.

Agree with Dr. F: You may watch and wait. If any of the nodes more than doubles in size, ulcerates, bleeds, your son loses weight or develops fever, see a doctor. Wish you and your son good health!