Moving back into a cot help

I have a 14 month old son who has slept in his cot since 6 months old. When he’s Ill he will sleep in mine and my partners room.

Well he had a cold for 2 weeks got rid of it for 2 days then got another cold. We have tried everything in the book

-leaving him to cry (not to long or he’s sick)

- staying in the room till he goes to sleep he won’t go to sleep

He just won’t have any of it and I’m stuck on what to do to get him back into his cot

Can any mamas help me out please