Hopefully you have not done any serious damage, diesel fuel is the lubricant for the injection pump and injectors, petrol is far to dry and serious damage can be done if the engine attempts to run on petrol, also if a petrol / diesel mixture is used you can also do serious internal engine damage, i have seen cracked pistons as a result of this, you will have to get the tank drained and flushed, flush the fuel lines, replace the filter and re bleed the pump and hopefully no damage has been done.