Sis went to doc for lymphnode below ear. doc says to watch for 2 weeks. sister has had gum infection recently but nothing else besides bad allergies. shes 21. node has been around almost 2 years but only recently enlarged then shrunk. is it urgent?

That is what lymph nodes do. Like an Army barracks it enlarges if there is infection near it (by the ear could be throat, sinus, neck, ear, skin) so a ton of white blood cells are in the vicinity fighting it. Also, if you find a node and then irritate it (like checking it often) it will stay enlarged or may even grow. Two years at your age likely OK, but ask your Dr to look (non-urgently).