First of all, mini black holes at the LHC are an option only if one of the theories of "large extra dimensions" would in fact be true. But of course, these theories are only speculations so far. Second, should mini black holes be created in high-energy particle collisions, they would evaporate very fast, due to Hawking radiation. Though Hawking radiation has not been experimentally verified so far, its existence is expected in almost all theoretical scenarios investigated (no matter where you go, you will always find somebody who disagrees on something).

In short: If tiny black holes were produced because large extra dimensions did exist in the necessary number with the necessary radius, and if they did not evaporate within 10-26 seconds as expected (Hawking evaporation is considered a very robust prediction, so this scenario is not confirmed by well founded theories), most of them would have such a high velocity that they escaped the gravitational field of the Earth for good. Even if they travelled straight through the centre of the Earth, the few nucleons they can hit wouldn't change their momentum in an appreciable way.