[Caprig]

So I had a slip up and my front brake lever snapped.I ordered a new one, now when replacing the lever with the new one i came across this black screw that pushes on the button. Its a pain to take off and the new brake lever didn't come with one of those. Do any of you guys know what it is called and how to remove it? I've tried using an allen key but it didnt work and also tried to use pliers to loosen it and its still stuck. I hope I don't need to order one of these.