Grand juries fail to indict less than 0.1% of the time, not exaggerating. Furthermore the (female) judge dismissed this case with prejudice, meaning she can't refile the charge, and basically called out the plaintiff for wasting police resources. It's rare for a judge to call out the plaintiff in their decision, and damn near unheard of in domestic violence cases. The plaintiff also now has virtually no chance in a civil suit. Nick, on the other hand, could sue her for defamation and probably have a pretty good case (although probably he doesn't want to deal with that shit and I wouldn't blame him in the slightest).
This woman changed her story, and the doctors who treated her found no injuries, bruising, or lacerations that were consistent with her story. So basically Nick is innocent.
If I were him, I'd request a restraining order against the other party and also file a petition for a Statement of Factual Innocence.