Baby is able to flip today, from back to tummy. He is not able to flip back yet. I'm concerned if he will flip over on his tummy when he sleeps at nite? He slps on his back at nite.

Remove everything in the area. Most of the times, things happen due to the pillow or blanket suffocating them. I would clear everything away. Babies who can flip will usually cry if they need help or are feeling uneasy.