Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services for:
Trouble breathing, choking, collapse, or reduced alertness
Severe chest or abdominal pain
Vomiting blood or passing black or bloody stool
A swallowed button battery
Severe eye pain or sudden vision loss
Extensive burns of the face, mouth, or throat
And for anyone, someone who:
you believe has taken an overdose or swallowed something poisonous
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
2
Is any of this happening?
Be seen today
Get urgent medical advice immediately if any battery may have been swallowed.
Treat a missing button battery as a possible ingestion, especially if a child has unexplained drooling, coughing, vomiting, or feeding difficulty.
Contact a poison information service promptly after exposure to leaking battery contents, even if symptoms seem mild.
Have the packaging available if it is safe and easy to obtain.
The article also says
Attend all arranged appointments after an internal burn or battery removal.
Seek earlier review if swallowing becomes harder, food sticks, vomiting continues, abdominal pain develops, or a skin or eye injury does not heal as expected.
Every sign above is quoted from the sofidex article on Dry cell battery poisoning. If you are not sure, err upward — it is always reasonable to be checked.