Pain can be a funny thing. The source may be in one area, yet you feel it in another. Because the pain happened on the night of the flush, its a really good bet its related to the flush.
It sounds like you dislodged a calcified stone that didn't completely make it out of your liver. It may take a few flushes, but you should be able to get it out. Make sure you take the Epsom Salts to dialate your bile ducts.