Mac os not showing after install windows 10 with boot camp

I'm unable to switch windows to Mac os after installation of Windows 10. I tried holding the option key even the boot camp not appearing. how to get my Mac os back.

Steps I followed to install Windows in my mac using Bootcamp:

1. Updated to Catalina
2. Downloaded Windows 10 iso file in to downloads
3. Open > Boot camp > selected windows 10 iso file then finally installed windows
4. Windows successfully installed but Mac os not showing.

Kindly help.