One of Judge Dredd's trademarks is that he is never seen without his helmet. Over the years there have, however, been a few stories which have given glimpses of what might be.
This suggests that Joe Dredd is deformed, somewhere between the nose and hair-line.
This frame shows Rico and Joe side by side. Whatever deformity Joe has, it wasn't a birth defect.
Again, Joe is shown to have a normal face as a cadet.