Xperia M dual stuck at boot screen after unlocking bootloader!
I've solved my problem for myself by re-locking the bootloader and then repair the device using Sony PC Companion. Device is again in mint condition ;)
I'll add a supporting link later.
Support links-   

(1) How to get into recovery mode in Xperia devices?
(2) How to repair software using Sony PC Companion on Windows and using Mac Bridge on OS X?