It's crossbeak/scissor beak, the beak isn't aligned properly due to some deformity in the head. Usually gets worse as they get older, but you can try to help manage it by providing easy to eat food like wet feed in deeper dishes.
When you trim it, the goal isn't to fix it (you really can't) but to make it so the bird can still use its beak to some degree so it can still eat and drink. You only want to trim off around the margins of the beak - they're like cat/dog toenails, with blood vessels and nerves towards the middle that you want to avoid.