Tension knot or a lump??

Tonight I found a lump in my upper neck area, on the back of my head. Like between my head and my neck. I’m so worried about it. I don’t have health insurance but I should probably get it checked out by my primary doctor? Or make an appointment with some other doctor (neurologist??) as I don’t have insurance I don’t need a referral.

My husband said that it could just be a tension knot in my muscle.

I don’t know how to tell the two apart! It could be either or....

any way to distinguish the two apart? Should I make an appointment with primary doctor for this, a neurologist or...??