Pop him back in the cot hon! That's quite young to be in a bed. Our DD2 is 26 months and still in her cot at night. DD1 was in a bed at 20 months only cause she climbed out of the cot! I certainly wouldn't have moved her into a bed that early otherwise. Like you've described, our experience with DD1 was hell and it didn't really get easy until she turned 2.

I say if they're happy in the cot then leave them be