An armed security guard at a Walgreens in the Port Authority Bus Terminal says he was wrongfully arrested after he jumped in to stop a shoplifter — who allegedly clocked him in the head with a jar of food.

Retired NYPD officer Salvatore Lopiccolo, 50, intends to sue the Port Authority Police Department over the March incident that left him facing charges including assault, for allegedly threatening and “recklessly” causing injury to the accused thief’s back, according to court documents.

Cellphone footage provided to The Post shows Lopiccolo confronting the man at the store’s door and grabbing his bag. The alleged shoplifter swings the tote at the guard, cracking him in the face with it, the footage shows.

Lopiccolo then chased the alleged violent crook out of the store, throwing him to the ground and wrestling him until NYPD and Port Authority cops arrived.