Just use Flash Tool to re-lock back -
http://www.flashtool.net/
By the way, you already unlock, no point you re-lock back, it still warranty void and Bravia Engine 2 / X-Reality won't coming back for photo view in album even you re-lock back.
The Bravia Engine 2 / X-Reality only can remain if you had backup TA before, but since now the only root need unlocked the bootloader 1st, which means you can't do TA backup anymore as TA backup do need root access on device that never unlocked the bootloader for it.