If you tightened it up and the leaking stopped and your car is running fine no need worry on it.
If it is the one that goes to the #1 Cylinder; that is the one they would need to remove if they had retimed the Fuel Injection Pump.

If it is another one that was leaking there is know way to know. It is extremely seldom that loosen by themselves.

__________________
84 300D, 82 Volvo 244Gl Diesel