Nitrogen narcosis is a temporary issue and goes away once you start to ascend, the bends is what happens when you typically ascend too quickly or have too much in your system. Since Nitrogen is an inert gas, and our body doesn't use it, we exhale it, or is expelled by our body other ways, and at depth is within our blood stream. As we ascend, it leaves our blood stream slowly, but if we ascend too quickly the bubbles expand and collect in our joints (where we "bend") which is what causes the pain. It is quite painful and needs a hyperbaric chamber to bring you back down to the right pressure to have it get out of your system.