What is the chance of a black hole hitting the earth?
Quite literally, practically zero.
Within 10 light years of Earth, there are no suitable conditions for the formation of classical black holes. As in, there are no supermassive stars about to go supernova. So... no. There is zero chance of a black hole "hitting" the Earth.
In about 4 billion years the Milky Way will collide with the Andromeda galaxy. Due to the extreme distances between stars, however the chance of stars hitting will be extremely unlikely (imagine trying to shoot a single moving bullet with another bullet from a mile away). That being said there is still a very very small chance that during this time a black hole in Andromeda could get close enough to Earth to capture it.