injection pump leak

[jpliddy]

well folks this is the 1st leak ive had on my injection pump in 20 years of ownership ,
the leak is at the back end just behind the round disc with 4 allen ket screws
theres a 10mm nut which the accelerator plate turns on diesel is coming up through the nut area and seeping down both sides of the injection pump
sorry about the detailed names of the parts im not familiar at the moment .
question is can it be fixed easy i have pinched the nut up a bit is this wrong the
accelerator cable plate still moves freely .
just hope someone can help
regards jim