Encourage the person to keep coughing to try and clear the blockage. Ask the person to try to spit out the object if it's in their mouth. Don't put your fingers in their mouth to help them as they may bite you accidentally.
If you are experienced, you should help them. If you are inexperienced, get some help so you don't make the matters worse. Better safe than sorry, a quote that helps many people, including me.
