Pixelated images after preview

I couldnt see it on photoshop but once I uploaded and view as preview the black background(right photo) become pixelated in certain spot.
and it is more obvious when I view it on my phone :sob:
Not sure if it has something to do with the export setting. Thanks!

Hi! R/m converts JPGs to improve viewers experience. Try to upload PNGs (they aren’t affected)