My 19-month-old hates bedtime. If left alone for two minutes in the cot, he vomits. He gets so upset he shakes and is all sweaty. We went away two weeks ago and he slept with me and now here I am. Being firm doesn't seem to help.
I hope you have a bedtime routine, such as reading to your baby or rocking him to settle him down. Warn him when it's coming to an end. Set a clock to go off. Then you can return after a few minutes to sit and soothe him. But don't take your baby out of his cot unless you plan to repeat this action over and over again, this is my parenting advice. Your job (and his) is to help him learn to get himself to sleep. He won't like it but he does have to learn to separate at night. You can make it easier for your baby, but you can't do it for him. The second year is a difficult time for such bedtime routine transitions, but he can, and will, learn to sleep separately. Your supportive firmness will help him.