This will pass.....good sleepers almost always go back to being good sleepers.

There are a few things you could try.....the first is to light his room a bit.....we use 'fairy lights' which are just a 50-bulb strand of Christmas lights that we place on top of dd's armoire. It gives a glow in the room, not too much, but enough to see.
When my dd (also a great sleeper) went thru some fears, I sat next to her crib and held her hand until she feel asleep a few nights.
The best way, IMO, is to stay with him, build trust.....then one night tell him you have to pee, and you'll b

right back. Then come right back within a minute. Next night, same thing....tell him you're going to brush your teeth, then come right back. Put clothes into the dryer, and come right back. come back EVERY TIME, in just 10 seconds if that is what it takes to return BEFORE he gets upset. In time, I was able to tell dd..."You rest, I'll be right back to check on you in 2 minutes...." For her, just knowing I'd be returning, she allowed herself to relax, to roll over and in time, close her eyes. We still do the 2 minute check all these years later.
