Looking for a little reassurance

My son has slept with us since he was born. He’s now 12 months old and we began sleep training three nights ago. The first two nights he cried a bit but went to sleep and slept good. Last night on the other hand he cried for a long time and looked scared when he woke up this morning. I just don’t want him to be scared to sleep in his room. Is this just a leap in sleep training?

He has a small lovey his doctor okayed to make him comfortable, it’s a good temperature in his room, he always has a fresh diaper and cozy pjs, he has a night light and white noise, a humidifier. There’s really not much else I can think of to make him comfortable. He’s very familiar with his room too. We play in there all day. I just hope it gets better