Could be teeth or milestones! My son's sleep schedule is off right now because of walking, and this happened with all sorts of other milestones as well. (Including pulling himself up- very exciting!)
Assuming he's not sick, or getting a tooth, it's probably the pulling up. Your son may be unable to lay back down on his own. I would be very consistent about your approach. Go in, keeping the lights off. Don't talk to him very much, and no playing! :) Lay him back down, and gently soothe him. Then leave. Give him time to holler. If he is still crying in 15 minutes, repeat it. At that point, I'd let him cry! (If you're not comfortable with that, then stay consistent with whatever you choose!)
I wouldn't do this if he's teething though. Try motrin before bed. If that helps, then it's teeth. If not, assuming he doesn't have an ear infection (always a possibility!), then it just takes time. He'll learn to handle all this excitement...then he'll start walking and the cycle will repeat!
Good luck!