P.M.
They can take themselves to a doctor. An emergency room, if necessary.
It could be nothing more than indigestion causing the symptoms. It could be an inflamed esophagus, or an ulcer, in which case, aspirin would probably make it worse. It could be a panic attack. It could be a blocked artery to the heart – a heart attack, which won't get better with baby aspirin.
I hope you can convince this person to get medical help, fast.