cyst on baby's head?

So my baby has had this for three months now she's four months and the doctor noticed that at her four-month appointment and he said it could be a lymph node but I was looking it up and lymph nodes are not that high up what does this look like to you guys? I never said anything because I thought it was just the way she was born I didn't think I could be something bad you know? He said we would just watch it to see if it grows