Nicole Richie Goes To Jail...AND SHE'S OUT!

The Insider is reporting that Nicole Richie has checked herself into Paris Hilton's Lynwood Correctional Facility to begin serving her 4-day sentence. She already has a 1-day credit for the 6-hours she served when she was arrested.

Nicole was busted for driving under the influence last December. She was driving on the wrong side of the highway. She admitted to smoking weed and taking Vicodin for "cramps."

Nicole is currently knocked up with Joel Madden's baby!

UPDATE - TMZ is reporting that she is out! Nicole checked in at 3:15pm and was out by 4:37pm. TIME SERVED!