Four males attacked a 19-year-old man on Fifth Avenue and 41st Street just after 6 p.m. on April 14.
The group punched and kicked the victim and one of them stabbed him twice in the back, cops said.
The attackers fled south on Fifth Avenue.
The victim was treated at the hospital for a collapsed lung, head injuries and cuts.
Anyone with information can call the NYPD’s Crime Stoppers Hotline at 1-800-577-8477 (or 1-888-577-4782 for Spanish). Tips can also be submitted at nypdcrimestoppers.com or on Twitter at @NYPDTips.