I inhaled diatomaceous earth (labeled as silicon dioxide) to control insect issue at home, and have been coughing for two days with slight chest pain.

Not serious: Diatomite is an amorphous form of silica that is relatively non toxic. In contrast, inhaled crystalline silica is toxic, and Acute Silicosis from exposure to high concentrations can develop within a few weeks or several years after exposure. You may have incurred a mild irritation of the airway but not at risk for significant lung damage. Should your symptoms persist see your Dr.