Learn how to say Checked In correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word check in:
(intransitive) to record one’s arrival, as at a hotel or for work; sign in or report
(transitive) to register the arrival of (passengers, etc)
the formal registration of arrival, as at an airport or a hotel
(as modifier) ⇒ check-in time
the place where one registers arrival at an airport, etc