Your device is now stuck inside a 'Boot Loop'....You should be able to fix this by entering recovery mode and reseting your device.
To enter recovery mode you should -
First make sure to power off your device. > Then by pressing and holding Volume Up, Volume Down and Power Button all at the same time your device should enter recovery mode (Note that you should release all buttons when the Blu Studio 7.0 screen flickers) > Then navigate to the reset/format option (WARNING : YOU WILL LOSE WHATEVER YOU PREVIOUSLY SAVED ON THIS DEVICE..PLEASE REMOVE YOUR SD CARD BEFORE PROCEEDING) > After this your device should boot normally (it would take some time for the first boot to happen).