It dawned on me when I was Zwifting today that you didn’t mean the tail bone but the pelvic bones that actually contact the saddle. When Zwifting you put a lot of downward force into the saddle and that just puts more pressure on these bones. You most likely overdid it in that massive session so give it a little time to heal. If you have a
an upright position that might make it a little worse so try riding with a little more weight forward on your arms