Remove cam lock pushed the wrong way into Ikea furniture
Sometimes you can knock them out by striking the wood furniture next to the hole, either with your hand or with a hammer. If using a hammer, put a small piece of wood (like, a chunk of 2x4) against your furniture, then strike this wood. That way it won't mess up the finish on your furniture.

Just a few taps. Don't hit it so hard that you break your other connections! :)

Sometimes it works to hit the same face of the wood which has the hole drilled into it (right next to the hole). Other times it works if works if you tap the furniture directly behind the hole where the nut is buried. Give them both a try.