I Am A Certified Athletic Trainer At The College Level

I am a Certified Athletic Trainer at the college level and have a men's soccer player who presented with an almost perfectly straight line from his sternal notch to just below nipple level yesterday after practice. He has no other signs/symptoms. No pain or swelling on or near the line. The line is not raised at all. Today after practice the line extended to below his belly button. He has no seams on his clothes causing it. After the first day we just figured he got scratched or hit during practice but after today, I am stumped! Any help is greatly appreciated!