Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care rather than waiting for a routine appointment if there is a new seizure, sudden severe headache, repeated vomiting, rapidly worsening confusion, new weakness, unequal pupils, loss of consciousness, or trouble breathing.
Follow-up depends on the cause and the effects of the brain injury.
After hospital care, some people need repeat CT or MRI scans, medication review, wound checks, or appointments with neurosurgery, neurology, stroke, cancer, or infectious disease specialists.
During routine follow-up, report ongoing headaches, sleep changes, problems with concentration, weakness, balance difficulty, medication side effects, or changes in mood.
These concerns may need assessment, but they are not always signs of renewed herniation.
The article also says
Rehabilitation may involve physical therapy, occupational therapy, speech and swallowing therapy, and cognitive rehabilitation.
Recovery can continue over months, and progress may be uneven.
Families may also need guidance about supervision, return to work or school, driving, seizure precautions, and emotional or behavioral changes.
Every sign above is quoted from the sofidex article on Brain herniation. If you are not sure, err upward — it is always reasonable to be checked.