As an oiler/greaser at a sawmill, I run into this problem every day. First thing to do is remove the fitting and clean out the hole down to the surface. if all is clear, I put a new fitting in but only start it in the threads. Then grease it, next tighten the fitting down, this will push the old dry packed grease/dirt thru, repeat this procedure a couple of times until it works with the grease gun.If it isn't clear and you see the brass bushing you will either have to take it all apart to realign the bushing with the hole. I usually grind a drill bit flat instead of its usual 30 degree angle.Just be carefull not to keep drilling after all the brass is gone.
Lothar
