I've had blockages that have taken 2-3 days to clear. After a few feeds it seems better, though still tender, but then the lump returns.
Definately keep an eye on things and go to docs if any other symptoms appear.

You can also try feeding on your hands and knees, to use gravity on your side. that seemed to help a bit the last time this happened to me. DS really got a kick out of that too.