After a near miss for me one time I’ve taken to always putting a chunk of wood into the cavity before drilling/clearing a hole, just in case. It’s always going to happen at some point... doesn’t lessen the pain though.

Perhaps make a magnetic mount cover plate and turn the oops into the notch to pop it? Or, if you can bear to do it, make a new cover slightly enlarged on just that side and carefully rout the extra couple of mm’s to remove the gouge.