Boot Camp - Can Only Open Windows 10

Hello! When starting up my mac (holding option key to choose between the macos or windows partition) if I choose the windows one it boots normally into windows 10, but if I choose the macos one the screen goes dark - then a white spinning wheel appears briefly - and then the screen goes dark again and so on and so forth (if I hold option again during this process it goes back to the choice between macos or windows and I can boot up windows).

When in windows 10 the bootcamp icon doesn't appear in the taskbar, or in the startup task manager, or anywhere for that matter - so I can't boot into macos from windows.

I don't really care about data being erased, I just want my computer to operate using macos again. Thanks!