Ugh. They do go through that from time to time. Time to troubleshoot!
Is it teething? Then give him Tylenol before bed.
Is he napping too much?
Is he getting enough physical activity? I know with my son, this is usually the culprit. A couple days of not being outside and we have bad nights.
Is it time to just let him cry it out? We finally had to do this and I wish I had done it sooner. If EVERYTHING else doesn't work, make sure he has what he could possibly need (plenty of pacifiers, closet light on, his special lovey, blah, blah, blah) and tell him "It is time for you to sleep through the night. Mama is not coming back until morning, but you have everything you need and I'll be right next door" or whatever. It is miserable, but you will get through it.
Good luck!