Restart the computer and immediately upon hearing the chime press and hold down the OPTION key until the boot manager appears. Select your OS X volume's icon then click on the arrow button below the icon. Upon returning to OS X open Startup Disk preferences and select your OS X volume if you want to boot OS X as the default.
If you installed the Windows drivers from Apple, then in Windows you can change the boot system using the Startup Disk control panel that was installed.
If this is not your problem, then please restate it clearly.