Careful whom you let inside.

A robber punched a Hell’s Kitchen man in the face and snatched his cellphone — as he stood in his own home — after he absent-mindedly buzzed the crook into the building, according to police.

The 30-year-old man was at his place on West 49th Street near Ninth Avenue at around 7 a.m. Thursday when someone unexpectedly rang his buzzer, cops said.

He let the person inside and, a few minutes later, heard a knock on his apartment door, police said.

He opened the door and an angry man allegedly demanded money. When the resident refused, the suspect punched him in the nose and ran off with his iPhone X, according to police.

“If you tell the police, I will hurt you!” the man growled before bolting, according to cops.

Police later released video footage of the suspect, who was seen fleeing from the building while holding a cellphone and listening to ear buds.

The victim was treated at the scene for a cut on the nose.