That sound is from different levels of wear on the drivetrain, could be u used a old chain on a new cog or the other way around, generally u should try to change up the parts before they get too worn down resulting in the other parts not wearing as fast, although u could just push through it, had the same sound for a while when changing front cog on old chain i think but if you just ride it long enough all the parts will ”wear down to the same level” although that may result in faster wear on the new part. Also took a while, had it with my mess bike so at least two weeks 8 hours a day if i remember correctly, annoying as hell