Let him cry! I find most kids when starting cry especially when they haven't been away from mom much. Just let him cry and carry on with your day as if he wasn't crying. If he hasn't stopped in a couple weeks then consider that it might not be a good fit. I once terminated a boy after 3 days. He screamed like someone was killing him from the second mom dropped off until I called her half way through nap to pick up. He wouldn't eat or sleep. I managed 3 days and just couldn't stand it anymore (all the kids were walking around covering their ears).

Good luck to you.