If the fish didn't already have the problem when you purchased it, your decoration is the problem. Move your decoration further in the middle, if it is too much remove some of it. Your catfish needs to be able to swim comfortably around the walls and throughout the middle without being too much of an obstacle course or having to make sharp turns quickly. Raise up driftwood and other decoration so it can fit without struggling. The whisker will heal with time, but prevent future damage to catfish by fixing the decoration. You will know if you have fixed the problem by asking yourself this: If my catfish gets scared or is chasing live food, can it rush around the tank without hitting sharp objects or is too much stuff in the way?