My boy vomited suddenly, twice . Not caused by coughing. What should I do?? 21 months.

Don't worry a lot. The reason could be as simple as something your boy has eaten that his body didn't quite like. Kids also vomit when they are constipated or haven't passed stools for 3-4 days. Sit down and find out what the reason is. Meanwhile give your chid enough fluids to replenish the lost nutrients. If his condition still doesn't improve in a day, go see a doctor.