hello , as stated in your question you had head injury
,following which CT was done and it showed bruises in the brain.Wound was closed and now you have numbness
over the scalp
O.K,numbness may be because of injury to sensory nerves supplying the region since several stitches were put to close the wound,might be a deeper injury.Fourtunately sensation will return but may take too long may be weeks to months.When it starts to recover initially you will feel pins and needle kind of sensation.
Hope your doubt is clear , if not write to me.For further clarification consult your doctor.Get well soon.....