Is it ok to let my 15-month old "cry it out" in his crib at night?

My son and I had a bed time routine that used to work, up until about a couple of weeks ago. After he ate dinner I would play with him, then I would give him a bath, then let him play for another 10 minutes or so, read our usual bedtime story, and then I would turn his music on and put him in his crib and then after about 10 minutes of him talking to himself, he would fall asleep, with no problems. It used to be so easy for him to fall asleep in his crib. He would be so tired after a long day of playing at day care that he would reach for the crib almost immediately. But for some reason now, when we do the same routine, he will stand up in his crib and throw his pacifier on the floor and just cry. I do not know why his behavior has suddenly changed. It breaks my heart to hear him in there crying, and my husband insists that we should "let him cry it out" until he falls alseep. I am having a really hard time doing this. I know at 15-months he knows what he is doing, and by throwing his pacifier out of the crib and crying, he may just be testing me to see how or if I will respond. Last night he cried for about 15-20 minutes before falling alseep. Like I said, it just breaks my heart to listen to him cry. But I also feel like if I keep going in there, just to take him to our bed to fall asleep, then back to his crib, he will get used to that each night and expect it each night. I put him to bed around 7:45-8:00. Could it be that he's just not tired at that time? He takes about 1 1/2 hour-2 hour nap at day care after lunch time, so he is getting rest at school, and I know that if he gets TOO tired it's also going to be hard for him to fall asleep. He is just now getting over an ear infection, so that also might be part of it. I just don't know if it's good to let him cry it out and fall asleep or helping him fall asleep by either rocking him or lying down with him. Any advice would be great.