If it smells bad, IE smells like death or dying or decaying materal then its not cured at all. One simple way to test the cured status would be to put the rock in a temporary holding stank/trashcan/bucket with saltwater and a heater and powerhead. Come back after a few hours to a day and check for ammonia. cured rock should not show ammonia but uncured rock will.
If its uncured and it sounds like it is from the fact it has an odor then it will cure over the next few days/weeks. During this time your also cycling your tank.