An old adage is to not let a child go to sleep after having a serious fall or if they get hit in the head. Any serious fall or hit on the head should be discussed with your child’s doctor. Even if you think they will be alright, your doctor may want to see your child or give you information about what to watch for.
However, when your child has a fall or hits her head and you do not consider it serious, you only need to keep an eye on her for a while (about 2 hours).  After a serious fall or a hit to the head, it is fine for a child to sleep. In fact, a little nap may be just what she needs after a trauma.
You do have to watch your child for a couple of days for any signs of damage such as headache, vomiting, speech changes, trouble coordinating or walking.
Also, it’s recommended that you try to wake your child a couple of times during the night and check for the ability to walk and talk. If you cannot wake your child, or you see other worrisome symptoms, seek medical attention immediately.