Help! My 20 month old climbed out of kid crib

So today for the first time my son (20 months old) fought his nap so much that he climbed out of his crib. He did it again at bedtime. Normally I read him books, give him his lovie, put him in his crib and he puts himself to sleep. However today this was not the case! Please.... someone help me lol! I have my hands full with a 2 1/2 year old, a 20 month old (the crib climber) and a 1 1/2 month old! I refuse to sleep with him so any other tips would be greatly appreciated!