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 someone cannot speak, cough forcefully, or breathe.
Also call if they become unresponsive, develop blue or grey lips, or have rapidly worsening throat or tongue swelling.
If the person becomes unresponsive, place them on a firm surface and begin cardiopulmonary resuscitation, or CPR, following the emergency call handler’s instructions.
Do not perform a blind finger sweep.
And for anyone, someone who:
Arrange same-day medical advice if choking during meals is new or recurring, even if breathing returns to normal.
Seek prompt assessment after abdominal or chest thrusts because they can cause internal injury.
Book a routine appointment if swallowing regularly feels difficult, food sticks, meals take much longer, or coughing or a wet voice continues after eating.
Unplanned weight loss, repeated chest infections, or avoiding food because of choking concerns also need assessment.
The article also says
If the person can cough strongly and breathe, encourage coughing and watch closely.
Do not give food or drink.
Do not put your fingers in their mouth unless you can clearly see and safely remove the object.
For severe choking in a conscious adult or child over 1 year, use back blows and abdominal thrusts according to recognised first-aid guidance.
Use chest thrusts instead of abdominal thrusts during pregnancy or if you cannot reach around the abdomen.
For an infant, use back blows and chest thrusts—not abdominal thrusts.
Every sign above is quoted from the sofidex article on Choking. If you are not sure, err upward — it is always reasonable to be checked.