welcome.
that’s a fisheye lens. you’ll need to work with the fisheye model. OpenCV has a bunch of routines for that.
if you can’t wave a calibration pattern in front of the camera, you’ll have to guess the parameters and see if they produce a sensible result. you can start by picking identical points on the field and on the picture. that’s equivalent to calibration (but not nearly enough data for a good calibration).