Hello. Thanks for asking from HCM.
I can understand your concern. As per your history, you are having multiple episodes of head injuries. It might have lead to 
concussion. Concussion means 
head injury without detectable lesion like fracture or bleed, from blunt object which manifests as headache, memory impairment, episode of 
loss of consciousness, vomiting. It is a treatable injury and resolves with time. Your persistent headache may be due to concussion. Rare chances are that it might be due to fracture or bleed below skin (scalp hematoma) or clot in brain. 
You can take 
Diclofenac sodium tablet for relief. Take the drug after prescription only. Avoid hitting your head again. If pain still persists and increase in severity, occurs with vomiting or loss of consciousness, consult neurosurgeon. You might need CT scan of brain. 
Swelling is due to edema of 
soft tissue and small amount of blood in skin layers. It resolves on its own in 14-21 days. 
Thanks. Hope it will help you. Take care.