It’s so small at that point it begins to act a little like a white hole (Hawking radiation iirc?) and evaporates quickly. It’s surprisingly difficult for matter to cross an event horizon.

Edit-actually having a small black hole would unlock some truly sci-fi sounding tech. Like the fastest interstellar travel, seemingly unlimited power, etc.

If they manage to create one with almost no velocity, it would keep falling through the Earth, down, up and down again, for either something between atoseconds or centuries, until it either explodes or hits enough matter to get big enough to matter.

Or, more realistically (as realistic as we can be talking about the LHC creating black holes, AKA, not realistic at all), it will be launched into space in some random direction.