Untie or Tickle?

My boy 'c' thinks I'm about to untie him and let him straight down after his whipping, but I have other ideas. After 'c' discovered a very ticklish spot on Mistress recently whilst tending to his slave duties, I reprimanded him instantly, however in this moment I had a wonderfully sadistic idea mid-scene to enact a little revenge on his pitiful body. He should think himself lucky he got away easy... this time.