9 week old has swollen lymph nodes

My 9 week old was just laying on my chest and I felt a pea sized moveable lump behind his ear. I realized it was a lymph node and when I felt around I could feel 3 more. I’ll be calling the doctor first thing in the morning but I am panicking now! He doesn’t have a fever or anything but he did get immunizations earlier today so not sure if that is the culprit. Anyone else’s little one ever have this?

My mind is wandering and I definitely won’t be sleeping tonight 😭