Hi,
before my rib resection when I used to walk all my fingers inc. thumb would swell up and turn a purple blue like a bruise. They were like fat sausages. Horrible to look at. They settled with rest and the pooling blood went away as soon as I took my arm up a bit and let it decrease in size. I was horrified by this but it did go away after rib surgery. Only happens now in extreme cases of swelling and compression....or if I do waaaayyyyy too much like we all do from time to time!!
hope my experience helps you figure out what is going on with you!!

take care
love and hugs,
Victoria