Has anyone his the disfortunate pleasure of diving with a bad bruise/ knot (about 3 inch in diameter)? Is it a health risk? We are going in three weeks and I am not sure if I need to postpone our trip.

Hi Clay,
I've been diving with smaller bruises and have never suffered any untoward effects, but never with a bruise the size you've described.
It would probably be a good idea to contact the folks at DAN for their expert advice. They're really super. After my rotator cuff surgery, I wrote to them to ask about the risk of DCS due to scar tissue and such, and they not only gave me good advice, but they published my letter and their response in 'Alert Diver' magazine and on their website.
I wish you good luck and safe diving. Robyn