Found an error in the title of published article (A phrase has been repeated twice)
Send the journal's editorial office a note and let them know. 

I made the a similar mistake once with one of my first paper after the paper had been published online (the paper had a misspelling with one of the words and my department's admin staff caught when preparing a departmental highlight). The journal was happy to fix it, even though I had already returned the final version of the manuscript and they had published the article online. I suspect the editors did not want to have a typo in an article title in their journal.