Small knot on back of neck

Hi,
I have a small knot on the right side of the back of my neck about 1 1/2 inches down from my hairline. It doesnt move but is somewhat tender in pain when I touch it, but not very painful. Rating the pain from 1-10 with 10 being the worse in pain, I give it a 2. I discovered it just yesterday and was shocked of course. I am a little worried about it and wonder if it is anything I should be worried about. My husband says we should monitor it for a few days and if it becomes larger or pain increases that we will see a doctor. Is it common for a knot to form on someone's neck? What could the knot be? Should I go to a doctor immediately? These are my concerns and what do you advise? Thank you so much for your time.