[Wordpress issuses] qiujinhai on "Change my name back..."

Hi, yestoday I changed my name from Gimhoy to Qiujinhai, I now hope to change it back, how can I do ? I try to register a new account, but it said Gimhoy has been used...Thanks for your help!

The blog I need help with is qiujinhai.wordpress.com.

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