Hey there Hannah, Welcome to HCM,
Well seems like you've been whacked pretty badly. Generally the bump,
bruise and soreness happens after even mildest form of traumatic
brain injury.
Since its been a month and you havn't mentioned any other problems apart from the bump and soreness, I guess you need not to worry too much. Perhaps try applying some ice-pack over the sore area(even though it's been a while since the injury).
Bumps and soreness generally get resolved within a few weeks but in some cases due to the nature of the impact , it takes even a few months .
So you need not to worry too much and all you need to do is keep an eye over the size and discoloration of the injured area , and if you notice any further increase in the size of the bump even after few days , then you may need to check into your nearest ER and probably get a MRI-Brain done.
Hope this'll solve your query, thanks a lot for contacting HCM