Unless they found an actor with a really flat/small nose they could credibly cover with prosthetic techniques, getting rid of a nose requires motion tracking, rotoscopy to remove the real nose and CGI prosthetics to replace it. That's perfectly feasible and even reasonable nowadays (that's what they did for Voldemort, for e.g. - there was no classic make up involved for the snake-ish face, just the actor looking like he had a really bad encounter with a porcupine) but it makes filming those scenes longer and more technical (you need VFX staff on set to make sure the crew doesn't film anything that will complicate the post process or cause a re shoot to avoid the VFX going over estimate), and thus more expensive because filming those shots is slower - not to mention the extra post budget. When you have the budget of Harry Potter that's a small thing to do, but on a TV show with a minor recurrent character you really ask yourself whether it's in any way important before spending VFX budget on details like this when you could keep the money for scenes where it pays off with the audience. They should still have done a scarred nose of some kind with make-up though (I tend to agree the show would have gained from giving some of the side characters more distinctive features like scars etc.)