Actually, no. This is a myth that has been perpetuated as long as I can remember by movies and TV.
The actual way to deal with what seems to be a rather minor head injury is to make sure when the person goes to sleep, to check on him periodically in the beginning to make sure he can be aroused and hasn't slipped into a coma.
It's natural for people with head injuries, even relatively minor ones, to be sleepy. Unless there are symptoms of a more serious nature, like being unable to carry on a conversation, or an inability to walk without difficulty, it's advisable to get rest and slee