Hi,
Welcome to ehealthforum,
It is difficult to comment on the cause for the bump on head that you describe without examining it. If it has been persistent, and symptomatic, you should consider getting it examined by your doctor/healthcare provider. Based on the examination findings, further investigations might be carried out to look for the underlying cause. Treatment as appropriate (based on examination findings and investigations results) would be started to help you control the symptoms. Be in regular monitoring and follow-up with your treating doctor/ healthcare provider and report any new/abnormal symptoms immediately.
Take care.