I heard in a daf yomi shiur (on kedushin 21b) that a koen can not want to stay a slave (one opinion says it is because he the Ear Piercing will make him have a mum
What Ear Piercing makes a mum?
Does a girls usual Piercing make her have a mum?
Did the Piercing that was given to a slave close up? (If yes did that remove the mum)
Related Getting body piercings