blocked duct- how long will it take to clear?

[allycat06]

So yesterday i was wearing a bra that was a bit too tight which i meant to take off once the washing was done, but of course I forgot and fell asleep in it. At about 4 this morning I remembered and took it off but it seems the damage has already been done, my right breast is very tender down one side and underneath. I've been feeding DS off this breast all morning, using a heat pack and trying to massage out the lump but it doesn't seem to be any better, once I have fed DS one side is soft but the blocked side remains hard and tender. Just wondering, if I keep all of this up how long it will take for the blockage to clear?