I can't view pictures I've taken I the stock camera app. I see the last picture on the bottom right, but nothing happens when I click it to open the gallery.
Welcome to Android Central! If you exit the Camera app and tap the Gallery app, can you see the photos? Are the photos saving to Internal Storage or the microSD card?
Most phones (except for Nexus phones) have a Gallery app. (The Nexus phones have Google Photos as the default gallery app). Go to Settings>Apps>Disabled and make sure you didn't disable Gallery at some point. If there is no Disabled list, then look at the All list, at the bottom.