Small lump on the back of my head

Hi, I have noticed a small walnut sized, hard lump on the back of my head, at the very top of my neck. It isn't painfull or sore and never causes discomfort. It's been there for as long as I can remember, which is probably around two years or so but I have only just began to think that maybe I should get it checked out, just incase.
I don't have any recollection of banging my head or hitting it at any point either, so I was wondering if it's worth going to the doctor's or not? Thanks, James.

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I have the exact same thing on the back of my head i read what u wrote and it siunds like the exact same thing i have on the back of my head and i have been worried about it so im going to the doctor to get it checked out Monday.