Have a poke about through the hole , you are feeling for a grease nipple. A mirror on a stick is also useful. You might have to rock the car backwards and forwards a little to locate it. Then Get some high pressure blue grease from JCB, about £3 per cartridge.
If its rattling you need about 20 pumps from a side lever grease gun. That will sort it out.
After that 10 pumps every 1500 miles or so.
I have done 8000 miles doing this with no problems at all.
