Thank you for posting your query.
The bump on your head, occurring a year after the fall, is most likely not related to the fall.
The alternative diagnostic possibilities in your case could be sebaceous cyst (infected or otherwise), a lipoma
(collection of fat), or a small hematoma
(due to minor injury
, which was unnoticed).
A clinical examination of the area would most likely sort out the issue.
Dr Sudhir Kumar MD DM (Neurology)
Senior consultant Neurologist
Apollo Hospitals, Hyderabad