First, the collider is switched off, which is why we can go there and see it (otherwise, no way for a human to go down there). Second, there is actually a theory that predicts the creation of black holes at the LHC. But the same theory predict that those black holes will evaporate in nanoseconds. So, there is no worries to have.

One big confusion with black holes is that there are two ongoing processes: matter accretion (the black hole grows) and Hawking radiation (the black hole evaporates). For small black holes, the latter dominate and the black hole's lifetime is tiny. For monsters, the former dominates and the become larger and larger. However, with the energy available at the LHC, only tiny ones can be created (mass = energy: we cannot produce more than what we inject).

I hope this clarifies :)