My Apple Watch's screen zoomed in and won't go back to normal size

Controlling Zoom

Once you’ve turned on Zoom, you can perform these actions on your Apple Watch.

• Zoom in or out: Double-tap the Apple Watch display with two fingers.
• Tip: Double-tap with two fingers while setting up your Apple Watch to get a better look.
• Move around (pan): Drag the display with two fingers. You can also turn the Digital Crown to pan over the entire page, left-right and up-down. The small Zoom button that appears shows you where you are on the page.
• Use the Digital Crown normally instead of panning: Tap the display once with two fingers to switch between using the Digital Crown to pan and using the Digital Crown the way it works without Zoom on (for example, to scroll a list or zoom a map).
• Adjust magnification: Double-tap and hold with two fingers, then drag your fingers up or down on the display. To limit magnification, open the Apple Watch app on your iPhone, tap My Watch, go to Accessibility > Zoom, then drag the Maximum Zoom Level slider.

From: Apple support's online article: Use Zoom on Apple Watch - Apple Support

Try to use Siri to “turn off zoom”