Ex-NFL star Jamal Anderson is back behind bars ... stemming from a bizarre incident at a Georgia gas station when the former Falcons star allegedly whipped out his penis in front of the clerk.
TMZ Sports broke the story ... Anderson was issued a criminal trespassing ticket for the incident -- and now we've learned a warrant was issued for his arrest because officials believe he violated his probation.
Turns out, Anderson was on probation from a 2014 DUI conviction -- and part of the probation required him to stay out of trouble with the law.