Re: blocked duct
What you describe sounds like a nipple blister (http://kellymom.com/bf/concerns/mother/nipplebleb/) combined with a bad plugged duct that got close to turning into mastitis (http://kellymom.com/bf/concerns/mother/nipplebleb/). I don't know how long you can expect to see the red patch, because healing is diffent in every mom. But I do think you need to be extra careful to watch for mastitis symptoms- return of the plug, increased redness/red streaks, pain, fever or chills, aches and pains.
Since you're dealing with a possibly plug-prone breast, I would advise against sleeping in a bra. Anything that puts pressure on the breast is probably not your friend at this point, since plugs often spring up at pressure points generated by a bra. Underwire bras are notorious for causing plugs. So for sleeping I'd advise using a towel under your chest area, and maybe a waterproof pad under your sheet.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"