UFC's Michael Chiesa Files Police Report Against Conor McGregor After Bus Attack

One of the UFC fighters Conor McGregor injured during his window-smashin' bus attack at the Barclays Center has filed a police report against the Irishman ... TMZ Sports has learned.

Our sources say Michael Chiesa -- who was hospitalized with facial lacerations -- spoke with cops at the arena after the incident on Thursday ... and again when they visited his hotel later that night.

Of course, Conor was also arrested late Thursday night ... and charged with 1 count of felony criminal mischief and 3 counts of misdemeanor assault.

We're told one of the assault charges is for injuring Chiesa ... who was forced to withdraw from his fight vs. Anthony Pettis at UFC 223 as a result of his injuries.