I see a small lump on my so neck on the left side it not painful hes not sick but he did have a history of sinus hes 14 yrs old it is dangerous?

Lymph node: There are thousands of lymph node located around the body that help screen out germs in the body serum. There are many in the neck, head ; behind the ear. At rest these are often 1/4 inch in diameter and may grow to marble sized when reacting to a stimulus. Bug bites, or viral infections can increase their size.They should shrink down to nl size over a few wks if pain not gone then have it chkd.