You may have had the metal drop out with the high chlorine level. You can remove the stain by using ascorbic acid, which can be bought online at:

http://www.msm-msm.com/store/agora.c...scorbic%20Acid

or:
http://www.chemistrystore.com/Ascorbic_Acid.htm

When you use the ascorbic acid, you must also use a sequestering agent, such as Metal Free, or Jack's Magic, Sequasol, or any product that says it suspends metals in the water. The ascorbic acid will bring the metal that precipitated out of the water and landed on the surface of the pool back into suspension. Then the metal free will hold the metal in the water. You will have to bring the chlorine level down in your pool before you use ascorbic acid, because the chlorine will use up the ascorbic acid, and you will need more to do the job. There are products to take the chlorine out, or you can wait till it comes down on it's own. The ascorbic acid will bring down your ph, so you don't have to worry about that. If you decide to use the ascorbic acid, I will help you do the process. THere are also other products on the market that will do the same thing. I have found the ascorbic acid works well for me and is cheaper than the others. Feel free to ask any questions you may have.