Could Swollen Lymph Node Near The Ear Be A Matter Of Concern?

I have a 3 yr old son and and a little bump popped up on his temple and couple weeks ago and its still there it almost looked like a small pimple or maybe a small scratch. Well 4 days ago I found a quarter size knot on his face right in front of his ear. I took him to the er they said it was a swollen lymph node . It s still getting bigger. When the doc left the room the other night she had said it was a rare one to swell and she had never seen it like that . What could cause it and since it s getting bigger should I take him back