The best possible action for you to take is nothing. Leave the incubator closed and don't open it. Chicks survive very well in the incubator for two days without food or water. Let it hatch naturally. Many times hatching is an all day affair.
I went through this yesterday. Paniced just like you. The advise I got was to WALK AWAY. What you are seeing/hearing is normal. Extra humidity is the thing to do. Also, as one person reminded me yesterday, a chick can drown in a bowl of water so make sure yours is a chick waterer or is very shallow.
Hang in there! Sounds like everything is as it should be.