I don't see the appeal of playing / practicing with jewelry. I agree with TR that a bad hop to where ever should be able to cure it once the find out it hurts a lot worse - if not then they deserve what they get.
My players will never wear jewlery once they step foot onto the field or have the uniform on. That is my area and my rules. If they don't like them then they can leave. Once they leave the field or are wearing their own clothes then I could care less what kind of jewelry they wear. As long as they are bringing negative attention to the team they can wear all the jewelry and clothing they want. But once they do something that makes the team look bad then we are going to have a discussion.