Thanks for writing your query.
After reading your post, it seems that the bump on your husband's head is a soft tissue
swelling and is a common finding after head injury
Though ice packs will help in decreasing the swelling, it will reduce in due course of time.
It usually takes few days to weeks for complete recovery.
You can give him pain killer like Ibuprofen one tablet twice a day after meals along with an antacid like Omeprazole
You should feel concerned if following symptoms appear :-
1. Loss of conscioussness.
2. Nausea or vomitting.
4. Difficulty in mainataining the balance of the body.
6. Loss of memory.
7. Nasal or ear bleeding.
If any of the above mentioned symptoms are not present and the MRI is normal, you should not worry.
I hope this is helpful to you.