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 if you have:
Severe difficulty breathing or cannot speak normally because of breathlessness
Blue, grey, or unusually pale lips or skin
New severe confusion, collapse, or difficulty waking
Severe chest pain
Signs of an obstructed airway, such as being unable to breathe, speak, or cough
A choking obstruction is an immediate emergency.
Use appropriate first aid if you are trained and call emergency services.
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
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek prompt medical advice if you develop a new cough, fever, breathlessness, chest discomfort, or unusual confusion after choking, vomiting, or a suspected aspiration event.
You should also seek advice for repeated coughing during meals, a wet voice after swallowing, unexplained weight loss, or recurring chest infections.
Contact the treating service promptly if symptoms worsen during treatment, do not begin to improve as expected, or return soon after antibiotics are finished.
Every sign above is quoted from the sofidex article on Aspiration pneumonia. If you are not sure, err upward — it is always reasonable to be checked.