Begin talking about it with him, and discuss with him the fact that you are searching for another one for him. Talk it up in every way you can—he will have new teachers, new toys, make new friends, etc. Take him with you when you go to visit other facilities. And, if possible, have some of the other mothers and children join you in the search. If one or two of his friends from the old facility can transfer to the new one with him, it will be a big help.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.