The symptoms of food inhalation depend on the degree to which the food is irritating. A bone or chili pepper would be much more irritating than a cheerio. The lungs are able to remove foreign objects. In fact, the cheerio has probably already been broken down and carried away by your body. However there is no guarantee of that. Inhaled foreign objects can cause irritation and cough. They can even lead to infection, but a bland food such as a cheerio is unlikely to do this.
Unless a cough persists or recurs or fever or discolored phlegm occurs, there is probably no need to seek medical attention at this time.