As NO and O3 react to create NO2 and O2, the concentrations of NO and O3 decrease (since the reactants turn to product), and the concentrations of NO2 and O2 increase. The equilibrium will shift to the right, but as time goes on, some of the NO2 and O2 will dissociate to create NO and O3 again. You reach dynamic equilibrium when the reaction rate of NO and O3 combining is equal to the reaction rate of NO2 and O2 dissociating.