The tiny piece you're holding in the picture is not a piece of fabric, it's (for lack of a better word) a "braid" of threads that extends from the seam. This is a very common thing in cheap fast-fashion garments because the underpaid workers don't care (and aren't paid) to finish their seams properly.
If you cut it too close to the actual garment, the individual threads will unravel and undo the seam.
Hack 1: The neat solution
Fold the protruding seam back onto the garment. Thread a piece of while thread through a hand sewing needle and start sewing over the existing seam in a zigzag. Start at the very edge of the garment and sew to a centimeter or 1/2 inch after the end of the protrusion. That new seam holds all the threads of the old seam in place and keeps it neat.
Hack 2: The lazy solution
Fold the protruding seam back onto the garment and glue it in place with fabric glue. If you don't have fabric glue, transparent waterproof glues like transparent acryllic may work as well. If all things fail, a tiny dab of transparent construction silicone sure does the job.
Be aware that all of the mentioned glues can leave ugly stains behind and stay visible after they dried. Many of them will not withstand washing very well (even most fabric glues slowly dissolve during laundry).