Hi.
Noted your short history about sudden
severe headache, development of small swelling on scalp, got reduced but still there.
The commonest cause of such an occurrence that I can think are as follows:
Hypertension spurt.
Migraine.
Vasculitis.
Local trauma, may be it was trivial hence you may not remember.
Rupture of a small blood vessel, cause to be found.
In such a case it is best to consult your Doctor as you need a detailed history telling, clinical evaluation, examination, blood pressure, relevant tests of blood and so on.
CT scan of brain and skull if needed.
Once a proper cause is found then a proper and specific management and further care can be taken for avoiding recurrence.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, ENT & General Surgeon