Same advice as others. Low flow, low light, and let it be. Make sure your Alk and Magensium are where they're supposed to be. Make sure nothing is picking on the coral and that no sand is settling on it. Once you get it in a low flow/low light area, leave it alone, for awhile, to give it time to heal. That's about all you can do, and hope for the best!
Good luck with it! Echinos are usually pretty resilient!