Thanks Skidroe, I just bought 11 tubes of grease (And a new grease gun). I'm pretty syre the thread is damaged (that's how came off) can you buy bigger thread grease nipples (I don't know how to pull the hinge pins out is this easy (i have limited tools, and knowledge too, i.e. no pullers, presses welders or blow torch). just some sockets, and a hammer
With your situation, I would start by removing the grease fittings (you are half way there!! - LOL), and clean the hole out below the fitting until you can see the pin, using a pick, a small screw driver, or a small drill bit. Flush it out really well with brake cleaner.
You will then have to repair the damaged thread. Since you say that you can get a larger grease fitting, I assume the one that was in there likely had a 1/4"-28 thread, and that you will be replacing it with one that likely has a 1/8" NPT (tapered pipe thread). If so, you will need to open the hole up slightly with an 11/32" drill. Try to go as deep as you can without hitting the pin. After you tap the hole, clean it out well, again using brake cleaner.
Install your new grease fittings and grease them up well. Operate the bucket a few times and grease it again. I would repeat this 4-5 times, until you have a clean grease flowing from between the pin and the bushing.
HTH