So worried!

L

My 18 month old has had a swollen lymph node on the right side of the back of her head for probably 4 months now, just on one side. She hasn’t been sick or anything. About a month ago, she had an appointment and her pediatrician said to watch it and if it doesn’t go away in 3 weeks, let her know. Well it didn’t go away, so now she’s having me schedule an ultrasound. Does she suspect lymphoma?! I’m so beyond worried. Anyone have any advice?