What do I do?
It is understandable that you should be careful that this shouldn’t happen again, but right now you don’t have to do anything. The reason is because we have a combination of lenient factors here, even if the water was indeed hot, it would only be iruy kli rishon, which would only have the capability to give apeels worth of taste. Coupled with the fact that there is usually very little actual milk inside the sponge, together with the factor that the soup according to many poskim would render the taste nosain taam lifgam. Therefore in retrospect, the utensils do not have to be kashered.
R’ Y. Cahen shlit”a