A YZ 85 doesn't have any grease nipples on it. You have to disassemble the linkage and steering head to grease the bearings.
That is indeed a bleed screw for the brake fluid, not a grease nipple. Odds are you only filled the bleed screw with grease, which may attract dust, but shouldn't harm anything unless it plugs up.
It would be a good idea to learn more about bike maintenance, and carefully evaluate the source, before allowing anyone else to do anything to your bike. Many people don't know what they are talking about, which could cause damage to your bike, when they do something wrong.