Indentations from furniture re-arrangement are a normal phenomenon in carpet. Sometimes, the situation is self-correcting in carpet cleaning. However if not simply place ice cubes in the carpet dips and wait a few hours or at least until the ice melts. Use a sponge to absorb the excess water, and then use a spoon or a coin to gently lift the carpet fibers.
Steam iron. For an entirely opposite approach, lay a clean damp cloth over the dent and steam heat with an iron.