As BricksUntold says, you can look at Photos' Setting>General and see the path to the Photos Library you are currently using. But if you have more than one Photos Library, then you can use the Library Picker to find the ones that Photos knows about. Just close Photos, and then Option-Click to bring up the Chooser:

This shows the path to each Library, and it identifies the System Library-- the one that other apps like Safari can be allowed to access. Make sure that the Library you use most is designated as the System Library! You can fix that in Photos' Settings>General:

"Use as System Library" will be grayed out if this is, indeed, the System Library.
If the Library is ill-formed, it may be that Photos doesn't recognize it. Then a good idea is to search for it with Finder search:

You can start by looking for things with the extension ".photoslibrary' which is on all Libraries made by Photos. If your aborted Library didn't get the right extension, then you might use the Finder to search for stuff you know.
As Keith Barkley says, once you find this errant Library, you can just drag it to the trash to be rid of it!
Let us know how it goes…