The centre-back was taken to hospital after suffering a deep cut, but the 27-year-old is now back in the squad for the return leg at the Emirates.
"Koscielny is fit and in the squad but I've not decided if I will start him or not," manager Arsene Wenger is quoted as saying in The Telegraph.
"It'll be stability in the team. Maybe one or two who are a bit injured, but 95 per cent of the team who played at Fulham will play. Jack Wilshere will play."
Victory in tomorrow's clash would see the Gunners through to the group stages of the Champions League.