Block::Block(int width,int height): myVector(width * height);{ // ...}
Or something like that. Then you can remove the implicit conversion to vector-of-vectors and replace it with an overloaded operator() (or a getPart() method, or something) that looks like:
int Block::getPart(int x,int y) // int Block::operator()(int x,int y){ return (myVector[x + width * y]);}
It will save you a lot of headaches in the long run.