I have a 2010 Nissan Ultima 2.5 ass it has a misfire in cylinder number four I replaced the plug and the coil pack is not bad according to AutoZone.what else could it be?

swap #4 injector with another, if miss moves, bad injector. Pray it's not a blown head gasket which those are known for as in this video https://www.youtube.com/watch?v=5zpNjYmmiYY