Mac OS won’t boot after Windows installed on a second hard drive

Hi guys, I’m hacking a problem on my boss hackintosh, i have installed Windows on a second ssd and now Mac OS won’t boot anymore from the bios It show the presence of Mac OS on the other drive but won’t boot anymore. There wasn’t a bootloader installed for dual boot soo i thought to start the os just via bios, but now only Windows is bootable, any suggestion? If u need some other info i can give u when i come back to my workplace.