Not sure what you are trying to do. Based on the subject of this thread you decided to post in, are you trying to get into bootloader? Or just trying to get the phone to boot to OS?
If you are trying to get into OS. You can try to wipe cache, and reboot to see if you can reboot back into OS (or factory reset and reboot, if you don't mind losing your personal data). But depending on what is wrong with the phone, you may need to do more to get into OS.