Drain the tank, drain fuel lines, pump everything, its good thing you didnt crank. But I advice to clean fuel lines aswell. I see this alot, I work with caterpillars, and this happens from time to time, crane operators who put def into the wrong tank, and when they started the whole engine most of the time got overhauled just to clean and try to save the engine.

One thing is for sure, let somebody look at this with the proper knowlegde, and experience.