Can not edit build.prop
Answering my own question as found the solution.
We can edit build.prop from mobile. I downloaded ES file explorer which is free. then from optin set "root explorer" and set "mount system as read/write" 
Now edit build.prop and save it using ES file explorer's editor then uncheck "root explorer" and "mount system as read/write" for safety..

hope it wil help someone :)