Hi there Binita,
it sounds like your Mac is booting but the screen is not turning on. I would recommend you use the troubleshooting for built in displays in the following article.
Apple computers: Troubleshooting issues with video on internal or external displays
It looks like all you have left to do is to reset the PRAM and attempt booting to safe mode to try and resolve it:
Start by resetting the Mac's parameter RAM. If the display does not come up, was previously set to an unsupported resolution, and still results in no video:
- Start up in Safe Mode.
- From the Apple () menu, choose System Preferences.
- Choose Displays from the View menu to open the preferences pane.
- Select any resolution and refresh rate that your display supports.
- Restart your computer.
Thank you for using Apple Support Communities.