What causes a moderately elevated ESR level with all other blood work normal?

I have a almond sized lymph node in my neck that has been swollen for like 6 months, so I went to the doctor about it. I have also been having a bit of a cold with green drainage, so they put me on antibiotics for 10 days. I went back for blood work and the doctor said everything looked great, WBC all metobolics and other levels were find, except the ESR level which was moderately elevated. She said she isn't too worried about it. When you look online it says lymphoma is often indicated by a high ESR. With me having that strange lymph node, now I am worrying. This is all turning me into a hypochondriac. So why would I have completely normal levels of everything but ESR. I feel fine.