That is a grease port yes. You can squirt a bit in there from time to time but a properly sealed/built front knuckle does not need it.
Keep in mind, unless you are running drive flanges and not hubs any part time Land Cruiser (40/55/60) front axle does not turn unless the hubs are engaged...
I think the OP already has the whole axle and birfield out at this stage.
One another note, RCV birfields like I have in my 80 series have a grease zerk on the end which allows you to grease grease them without pulling the axles out.
Martack. Search it.
That said, I pack the whole knuckle cavity with grease. There is enough in there that if there is a bit still in the birf that's a different type it's not gonna matter.
Ever