M.L.
I would start by putting him in his own bed after he falls asleep. If he wakes in the middle of the night, put him back in yours for about a few days or a week. If he does not wake up great, it was easier than you expected.
It DEFINITELY IS a transition where he will need extra reassurance and maybe even demand a little more attention from you when awake, so that he can know that you still love him and are not mad at him. So extra hugs, kisses, and words of affirmation may be needed during this time.
Then after a week, if he wakes in the night, reassure him he is ok and then if you have to, let him cry. Of course as always, make sure he has all of his essential needs met (diaper change, drink, pacifier, etc.) so that you will know for yourself that he really is only crying because he is not used to this new situation.
I have 6 boys, I had to eventually just let him cry. Crying will not hurt him, and it is good for him to get out some extra stress. You may need to put a pillow on your head.
Going in there 5 minutes, to reassure him,,, then add 5 minutes to make 10. Go in to reassure in 10, then the next time wait 15 minutes, and then the next time 20 , and so on, until he gives up! If you have a 2 way baby monitor to where you can talk to him instead of going in there, it makes this a lot easier and he does not actually have to see you, but just hearing you lets him know you care. This lets him know that you are still there, but gives him time in between each reassurement to wear himself down. This process may take 15 minutes or about an hour- depending on how determined he is and how determined you are.
It could take 1 or 2 nights or up to about a week, which means that you will lose a little sleep,,, so go to bed an hour earler if possible, but it will be WELL worth the night time inconvenience and feeling of tired. You may want to take extra naps during this transition period. Crying will not hurt him- trust me- as I said, I have 6 boys. They all slept with me, except 1 who did not like to sleep with me because he slept better in his bed and preferred it from birth. LOL.