What happens if you have an untreated skull fracture?

Not much: Almost all skull fractures are treated conservatively. They do not require treatment nor surgery. Most of the time the bone will heal. The only skull fracutres needing treatment are ones associated with bleeding or those in children which enlarge.

No treatment : For most skull fractures, there is no treatment. They heal over time. For more serious fractures such as compound skull fractures or full thickness depressed skull fractures, surgery is recommended. If a basilar skull fracture has a persistent CSF leak, treatment or close observation is needed. Bottom line...Seek medical attention for more specific advice.