I think you probably heard that in a movie. It's just playing with words. She said I love you brother, brother in Islam is how they called men, I hit the door with my head and.... I think the film name was Delshekasteh.

this sentence is a dialog of move and doesn't have any meanings the character of the move said this for befooling.

oh dear!! it is hard to explain but I try I love you brother! I go to the door (means hit the door), I hit the door with my head first, I caught a cold sister!