Version of InDesign? Operating system?
It's almost certainly a setting in your operating system which associates a type of file with the application to open it. On a Mac, you would set that in the File > Get Info command in the Finder. I'm only an occasional Windows user, so if that's what you're using, others will have to advise you.
In the meantime, you should be able to choose File > Open in InDesign and select the .indb file.
In Windows, when you (sometimes shift)+right-click an .indb file in Windows File Explorer, you can choose to change the filetype association via Open With...