Dont panic.
If you are dead sure the cam & crank are timed - then its the pump a bit off timing. This is however very easy to correct.
Have you noticed that the pump itself is mounted with bolts in slotted holes ? This is exactly to allow for pump timing with these bolts slacked and then turning the pump body ever so slightly in either direction.
Its a LOT easier than your present state of panic may allow you to think
Precautions :
The engine must be normally hot, indicated by the fan cutting in shortly.
The pump mounting bolts be slacked off, not dangling loose. Remember that the injector piping will resist the pump body to be turned, and tend to flip back the pump body.
Use any suitable tool to securely grip on the pump body for better hand torque when adjusting.
You can very clearly hear a change in the note of the diesel clatter from the engine. When it starts knocking heavily, you have the timing too far advanced. When the engine seems to be too quiet, the timing is too far retarded. Trick is to get the timing as close as possible to the heavy knocking, but with only the normal diesel clatter note.
When you are satisfied, then torque the pump bolts very carefully. Then re-start engine and check if the pump is still timing OK.
Finally : slack off all the rigid injector pipe unions and ever so slightly wriggle the pipes to remove any strain imposed by the turned pump body.
Good luck. X-ing fingers for you 8)
I once had a very lucky escape. The pumps vibrate quite significantly and certainly enough to shackle off a less than fully tight mounting nut.
