Reveal hidden files by typing ⇧⌘. (Shift-Command-Period).
Go into the folder named “.obsidian”.
Move the folder named “plugins” to somewhere out of the vault folder.
That folder contains the installed plugins and their settings. When you open the vault again, all of the plugins will be gone and you should hopefully be able to proceed. Then you can move the plugins back one by one (each has a folder in the “plugins” folder; you may need to make a new “plugins” folder in “.obsidian” if Obsidian hasn’t done it), restarting Obsidian each time, until you find the one that causes the problem.