Modern Warfare is rated at 17+. If your profile was setup to only play games rated below that rating, it will stop you from being able to play that. There are parental controls associated with profiles that can be setup to only allow certain profiles to be able to play certain rated games.

Disc installations on consoles\n\n Insert a game disc into your console's disc drive. The game will automatically install on PlayStation consoles. On Xbox consoles, you'll be prompted to install the game. Please note: Call of Duty: Modern Warfare II requires a Day One update in order to play the game.