Delete other disk from boot loader in Mac .

I used to install windows 10 in my Mac book air for playing Pubg mobile , this time I tried Prime os (android os ,from xda developers ,india) every this goes well until thought of reinstalling with some additional storage , I removed that disk partition of prime os directly from disk utility . there is where my problem starts even though I removed that prime os partition , while booting disk image of prime os pops up as shown in screen shot , this kind of situation usually happens with windows uninstall, I faced 2 times already , what I did I backed up my data and factory reset my Mac and installed Mac OS again . so I don't want do that again is there any way I could solve my problem without factory reset ..

please help me out

thankyou

in the below left one is boot loader for prime os & right is Mac OS (I forgot to change the name last time I erased my disk )