That'a how 'Create new block' works already. It creates a block in 'For this page' and then automatically adds it to the content area.
As stated in http://webhelp.episerver.com/latest/platform/blocks.htm, there are two ways to create blocks:
Which method are you using, SauravTanu?
Can we create a block for specific page only, so that block can not be used for other pages?
Clicking on "create new block" in a content area should lead the editor to "For this Page"-view, not all assets.