Hi there - sorry to be the bearer of bad news, but you will probably need to drain the tank, flush the fuel lines, and replace the injection pump and injectors. In a diesel system, the gasoline acts as a solvent and seriously reduces the effectiveness of the lubricating qualities of diesel fuel.
You could drain and flush the tank and lines first, and then see what happens. But chances are you will need a pump and injectors. You may wish to touch base with your insurance company to see if this is covered.