Okay slave, you're handling this pretty well. I'll let you untie yourself, but only on one condition.
You must find a way to get the buttplug out of your ass before you untie your hand. Maybe you can just push really hard, maybe you can hook it on an object, but you must try to empty your asshole without using your hands.
If you fail, fill your ass with no less than 10 ice cubes and do NOT empty it - EVER!