The fuel isn't "damaged" but is is likely contaminated with water. The unknown is how much. Most diesels have fuel/water separating filters and a warning light on the dash for water in the fuel. That's all because diesel engines do not like having water in their fuel system. You could run the fuel and hope your filter catches it. It probably will. Or, if it doesn't it might damage a very expensive part(s) of your fuel system costing thousands of dollars to replace.
I don't think I'd run it.