I think I need to take the cot side off

[Szeli]

DS 21 months can climb out of his cot. I'm scared he's going to hurt himself so I think the side must come off.
Problem is, my previously amazing sleeper; go in at 7pm cuddle and kiss and he shouts me at 9am, won't sleep atm. There's screaming and tantrums every bedtime.
The new routine is put in cot, ignore screams, put chill out music on and shut his door (previously left it open) which works ok.
I'm just scared if I take his side off I'm going to find him asleep up against the door or in the toy box. wwyd??