Personally, I would have gone for medium as the bruising is caused by not sitting on your sit bones but on the soft tissue inbetween. You may find with the small that your sit bones are still either side of the saddle, but see how you get on. You should notice an immediate improvement. If nothing has changed after a couple of rides swap for the medium. It may only be a few millimetres differences but it can be the difference between heaven and hell.