N.S.
It sounds like you have blocked milk ducts. This is and can really turn into a big deal, so you need to get on this right away, so it doesn't turn into anything awful like mastitis.
This can happen with 'sudden' weaning rather than gradual weaning, because your body gets accoustomed to producing and providing the baby a certain amount of milk (no matter how small the amount)and just because she stops, doesn't mean your body will know to stop producing. If you don't remove that milk that's building up, you'll get blocked.
When weaning, there is a process that involves gradually lowering milk output and also "binding" your breasts with a tight fitting bra. The pressure on the breasts helps with the slow-down/winding up process.
Considering it sounds like things might be getting serious. Hold off on the binding. Your goal now should be to get those ducts unblocked.
First, take a hot damp wash cloth and rest it on the breast. The heat from the washcloth will help you with letdown by helping to open the milk ducts.
Then, with a flattened, and stiff hand, with as much pressure as you can muster, begin to make downward strokes on your breast, toward the nipple area. The pressure and motion will force your ducts to release the trapped milk by flattening your breast with hard, downward strokes. While you should cover the entire breast area with your flattened hand, focus especially on the areas where you feel pain.
I'll warn you, this is alot of work. Keep applying pressure until you feel the ducts release. When the release happens, the milk should really flow. If you can not get enough pressure to force milk out, get help from your husband. When this happend to me, neither of us could get enough pressure. I came up with a remedy of my own.. I used a rolling pin, and it worked like a charm! I'm sure all who are reading this will think "weird!", but let me tell you, if things get bad enough (like they did for me...even the OB/Gyn couldn't get them to open up at the office so she sent me home to figure it out) you'll get to the point you'll try anything. I tell you, it works. After about half an hour of "rolling" the dough, I got rid of the blockage and things were flowing.
Once you get the release, and you are able to fully empty your breast, bind them in a super tight bra. Do this until you're certain milk production has stopped.
For temporary relief you can use cold cabbage leaves both while you have the blockage and after. The coolness feels nice, and there is something in cabbage that can help reduce the swelling. Just be sure that when you are about to try to unblock the ducts, you use a warm wash cloth, and leave it on the breast before you start working on it.
If you're havng a hard time picturing what I mean, go to the La Leche League website at www.lalecheleague.org and look up "blocked milk ducts" or "mastitis". They should have information on how to do this. Most books they carry on their webpage also have chapters on the subject with clear pictures showing how to do this. If you can't wait to order a book from their site if you should need it, you can get some of their books at most big chain bookstores. Their books have good picutures and explainations.
If you continue to have blocked ducts for more than a couple of days, you develop fever (even a low-grade one) nausea or flu-like symptoms, redness and hardness in the areas of have pain, or the pain is so bad you can't touch your skin get into the doctor's right away! You'll need antibiotics and more. Mastitis is serious business, so be watchful and ready if necessary. Hope this helps.
If things get bad enough, your OB/Gyn can help.