Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services now if a baby or young child may have been shaken, struck, or thrown.
Tell the emergency team exactly what may have happened.
Emergency help is also needed for:
If the child is not breathing, follow emergency dispatch instructions and begin infant or child CPR if you know how.
If you believe a child is currently at risk of being harmed, contact emergency services or your local child-protection service.
Move the child to a safe setting if you can do so without creating more danger.
Do not wait for symptoms to appear.
Routine follow-up is appropriate for ongoing developmental, vision, hearing, movement, learning, or behaviour concerns in a child who has already been medically assessed and is otherwise stable.
New seizures, breathing problems, or reduced consciousness are not routine concerns.
The article also says
Do not shake the child to try to wake them.
Every sign above is quoted from the sofidex article on Shaken baby syndrome. If you are not sure, err upward — it is always reasonable to be checked.