Help!!

Ok mommies.. Need some advice over here. Micah had been the best sleeper for pretty much since he was a month old. Last night we got thrown a curve ball. He usually goes to bed around 8-830pm and last night he was obviously exhausted so we put him down. He fell asleep but woke up maybe 30 minutes later and was crying pretty bad. It was very unusual so we went in and tried to figure out what was wrong. This went on until 10 pm. I changed him ..fed him.. Salined his nose.. Everything I could think of. We would go in and pick him up and he immediately stopped crying and was fine. Soooooo... I think he is finally starting to manipulate us. We let him cry and I mean scream cry (which almost made me cry) for about 20 mins until he finally went to sleep. Yikes. He is turning 16 weeks on FridAy. Is this normal? He is still taking good naps during the day without hesitation. I really hope this isn't going to be a new thing. How many Times do you have to let them cry it out before they learn. If it happens tonight at least we are ready this time.
Of course this happens the week before vaca. Hopefully we can nip it in the but before it gets bad.
Good news is he slept from 10:15 until 715 am. So that was nice.

Anyways here's another pic from swim class..