I would say the injector was dribbling or somehow leaking fuel into the cylinder. It may have caused liner wash removing the lubrication and causing scoring of rings. An earlier poster suggested a burned piston as well; again caused by un-atomized fuel on the aluminum piston causing overheating and deterioration (shedding, erosion). Eventually, the piston overheats and seizes. I suspect the piston is in many fragments and hard to peice back together.
I suggest at least cut open the lube oil filter and check for debris before running the engine again. Better yet, get a bore scope in the piston or from below and examine the liners before running this unit.
If you know the injector is bad then you know the fuel likely diluted the liner lubrication. This engine does not have any meaningful temp sensors to monitor so you have to play it safe. If you hear a noise don't start it again until you verify the source (if it's mechanical source, don't start until the repair is done). Otherwise you'll be buying at least a new block and probably a crankshaft to say nothing of the downtime.