"Boardwalk Empire" star Paz de la Huerta was arrested last night after she allegedly threw a glass at former "City" star Samantha Swetra at an NYC party on Sunday ... and then socked her in the face.



Sources familiar with the situation  tell TMZ, it all went down at the Standard nightclub -- after Paz and Samantha got into it over Samantha's male friend ... we're told Paz was hitting on him and Sam got defensive.

According to sources, Samantha made a few snide remarks about Paz's level of inebriation ... and Paz got PISSED, throwing a glass and punching Samantha in the face.



We're told pieces of the glass became lodged in Samantha's leg, and Lindsay Lohan -- who was there with Samantha -- helped pick out the bloody shards ... while Paz was escorted out by security.

Samantha made a police report this morning. So far, no charges have been filed.