You have vignetting. It's probably not from the pinhole failing to cover the film; more likely the pinhole is in too narrow a hole in the front panel material, and that material is blocking light from the pinhole reaching the film (or light from the scene reaching the pinhole).

I base this in part on the shape of the vignette -- if it were an exposure related vignette (as can happen if you don't account for the change in distance to center of the film vs. corners of the frame), it would be perfectly circular and the drop-off would be very gradual. In your case, the vignette has a distinctly non-circular shape and a moderately sharp edge.

Try opening your shutter and looking through the pinhole (at a bright background) from the corners of the film frame -- I think you'll find the light will be blocked. The solution to this is to bevel the hole in the front panel where the pinhole is mounted, so the hole doesn't block the light to the frame's corners.

From comments, I understand the pinhole here is just a tiny hole in the wood front panel of the camera. This would be improved by being drilled out to a diameter at least as large as the thickness of the wood, and mounting a piece of aluminum or brass on the back with the pinhole (0.1 to 0.5 mm diameter, depending on various factors) drilled in it.

What you have clearly forms an image, but it vignettes itself.