Questions about a fall and how long a hard bump should last?

My mom fell a week ago and hit her head. She has dementia. We took in for a CT scan the first and second day due to other concerns as well. Both showed good and no bleeding on the brain etc. The knot on her head is still there and really hard. Should I be concerned or how long should it take to go away. The big goose egg went away timely but there is a quarter size or so hard knot still there. Also, should I expect changes in her because of this fall even though the CT didn't show any significant concerns?