Did @DrBill‘s suggestion work for you? If not, it could be as simple as using the “Ctrl -” keystroke combination to return it back, just as using “Ctrl +” makes the screen zoom out. I use them fairly regularly. Sometimes it happens by accident when the left pinky finger goes for the “Shift” key and hits the “Ctrl” key instead.
@Pied_Pfeffer Yeah I got it thanks. I just installed the new OS and couldn’t figure out how to reduce magnification. And the Ctrl – thing wasn’t working. Thanks everyone! All good now :D