The fire broke out in at a jewellery shop on the top floor of a four-storeyed building in Lajpat Nagar's busy Central Market, officials said.
Six fire engines were rushed to douse the fire at Rama Krishna Jewellers, news agency ANI reported.
The injured person has been taken to the Safdarjung Hospital, according to a Delhi Fire Service (DFS) official.
"The call about fire in a fourth floor of a building in Lajpat Nagar-II's Central Market area was received at 8:55 AM," he said.
The DFS official said, "A fire officer got injured as a cylinder exploded while he was on duty there."
The fire was brought under control by 9:50 am, he said, adding that further investigation is underway.
Central Market has a number of shops and is one of the busiest markets in Delhi.
(with inputs from agencies)