2 year old has an enlarged lymph node in his neck. seems size of a small marble. not tender and no other symptoms. should i be worried?

Normal lymph node: We have lymph nodes scattered throughout our body ; many are often detected in the neck where they sit on top of neck muscles. These nodes are little fluid strainers that take body lymph ; remove stray germs from things like bug bites. They are often pea sized at rest ; grow to dime sized when working. Within 2-3 wks they often shrink back down unless they are stimulated further.Ask her doc if so.