One possibility is that this is just the normal bony bump at the base of your skull that is present in most people, but that you may just have noticed now. Excessive manipulation or pressure on this bump may cause discomfort, and this may be the source of your headache.
The other possibility is that you have a small cyst or growth under the skin in this area. If so, it is very unlikely that such a cyst or growth would be a serious problem or would need to be treated, as most growths like this would be entirely benign. The usual treatment is simply to watch them to see if they grow larger. If so, or if the pain worsens, they can usually be removed with a simple surgery that can be performed in your doctor
's office just with the injection of some local numbing medicine under the skin.
I suggest that you set up an appointment to see your doctors
">primary care doctor when able. They will be able to take a look at the bump on your skull and determine what it is and if it is something serious (highly unlikely) that needs further workup or treatment.