Forgot a piece of jewellery, should I complete the session or start over?
Yes it is a good idea to remove metallic items such as jewellery even half way through a session. Jewellery such as gold, silver or platinum are not a real issue. It is the costume jewellery and quartz battery watches that need the focus. There is no need to start over just remove the jewellery as soon as you notice it if at all possible.