racing IM with bruised ribs?

Well no where near the same thing (ie early season sprint training vs ironman) but I broke & bruised mine at the end of May.  I started back with a run a week and a half later and I remember initially it felt like I had a bag of rocks banging around my middle.  Pretty uncomfortable on the run with every step I took and I found that you subconsciously try to compensate for it which causes other discomforts (cramping, back stiffness) but within two weeks I was feeling better.  I also found that once I got past the initial discomfort I could go longer.  I considered wrapping something just to feel more solid but not sure it would have helped.  It didn't impact my cycling and I don't recall it bothering the swim (I had an elbow injury which impacted swim performance so hard to remember).  Just the run.  You still have a week to go - maybe some little runs to get used to the feeling and see if it's tolerable?  Hopefully it'll feel better closer to race day... Good luck and recover quickly!