Depends on where the water got through. If it went straight through the floor, that could be pretty bad. If it found un-caulked seems around the base of the toilet or tub, then that's an easy fix. You have several holes built into your floor for pipes to pass through. If it's following those paths, it's no big deal; just seal up your joints with caulk. If the leak was coming through drywall or floorboards, it may indicate a more serious problem and might also lead to mold.