black dot showing on every photo from my iphone camera

Same spot every time? That points to something physical on the camera rather than software. Give the lens glass on the back a proper wipe with a microfibre cloth first, and look closely for a chip or crack in it. Then switch between the lenses (0.5x, 1x and zoom if you have it). If the dot only appears on one of them, it's dust inside that module or a fault on its sensor, and that's an Apple repair, not something you can clean out yourself.