You can change, first. First ROOT your device.
Using file manager go to your root directory. Open folder named "system"system
. In that open file named "build.prop"build.prop
using text editor.
Search for option called lsd_display= lcd_display=
(after equals to enter your default DPI value) and save the file. )
Now Rebootreboot. Done.
Corrected spelling but most importantly changed `lsd_display` to `lcd_display`.