It could be a cyst. You should see your GP. They can remove these. It is best to get anything that is growing checked anyway.
Probably a cyst. It is fat that collects under the skin and forms a bump or knot. They can be removed. And removal process is not a big deal. They are in office procedures. As previous comment stated should still be checked. I have had GPs remove for me, but have also been told should be done by dermatologist. (I think the doc that referred me to derm just doesn't like to do much. I had no problems with the two removed by a my old family practitioner.)
i have had 3 simlple minor procedures done on my head due to small bumps that were cyts. it's symple, fast and painless. they numb the area and open the the bump and remove it. it can look like a oeice of rice or a garbonzo bean depending on the size. i have no pain after words eaither. no worries. they also do a byopsy on it.
A related discussion, Small knot on my head