Alek Skarlatos Breaks Nose in 'DWTS' Rehearsal

The bad luck streak continues ... Alek Skarlatos -- one of the French terror train heroes -- just suffered a broken nose, courtesy of his "Dancing with the Stars" partner.

Our 'DWTS' sources tell us Skarlatos and his partner Emma Slater were in rehearsals Monday morning when she accidentally hit him in the face with an elbow.

We're told medics are at the dance studio right now ... checking him out. Early prognosis is ... it's broken, but he'll have to get x-rays to confirm.

Just last week -- Alek's fellow train hero Spencer Stone was nearly killed when he got stabbed four times in the chest in a bar fight. Also, Alek was supposed to be at Umpqua Community College the day the shooting happened there -- but was at 'DWTS' instead.

Alek visited Spencer in the hospital just this weekend.