I Noticed This Morning, A Lump About The Size Of

I noticed this morning, a lump about the size of a nickel on the back side of my neck a few inches from my ear and right on the edge of my hairline, on the left side. It is hard and sore when I press on it. I don't remember having one before. I have a sore neck sometimes and now it is sore when I turn my head to the right. I am 68 years old and in good health for the most part. (Had arthritis in my 30's and still have some in my feet and hands. I am being examined for possible IBS. Having another colonoscopy this week to check that out.)
Any ideas on what this lump might be?