Shatcha blest

Means shut your mouth, or shut up.

If someone are saying/said something stupid/weird, you can say «shatcha blest» to make them silent, or make them cautious about the stupid/weird thing they are saying or said.
You can also use the saying against someone if they are doing/did something stupid/annoying/weird.

I told Johannes «shatcha blest» because he said something stupid that annoyed me.

I told Johannes «shatcha blest» because he did something stupid, or because he acted different in a weird way.