Yep, exactly what Fun&Care and mickyc said - let him cry it out! He doesn't know how to self-soothe after a sleep cycle and he needs to figure that out on his own. The other option is for you to go in every 5 minutes that he is awake to assure him that you are present, do not pick him up or even talk to him but gently lie him down, give him a quick hug and walk out of the room. you can extend this to every 10 minutes, then every 15 minutes, etc. in order to reassure him that he is not alone but to reinforce that it is time for sleeping. Babies and toddlers need to nap for their physical, intellectual and developmental needs. It will be a tough couple of weeks but remain consistent and it will work out!