hang a piece of sheetrock on it(no wider than stud!) and bead it. use that tape on bead junk since i doubt you have a "clincher". if you try to screw metal bead on you will end up tweaking it out of square. use plenty of fast set under that tape on bead and set it good. you want the outside corner(under bead) full for strength. easy job you should be fine. youtube the bead application.