Overload: Any bruise(a pooling of blood) will suggest a rupture/tear around an area, as well as a slight burning feeling sometimes. If getting that burning feeling when doing heavier chins, it's the adding weight allowing more stretch/stress on the region. Nothing to really be bothered with unless the matter becomes painful, advancing to a full blown injury. Extreme pumps have been know to cause this also.
Once worked out, for a couple of years, with a guy from the Shetland Islands. So white, and with natural thin skin, he almost glowed. Every workout his skin would become beet red, followed by assorted bruises after a workout. No problem, just the way he was. One of the fastest guy's, I ever trained with, to gain muscle mass and power....a true natural. That's counting all Polynesian's bro's, blacks, browns or everyone else. Reminded me of Yates, though a bit taller. Good Luck.
Side Bar: sorry, I told this story long before. Just some people, who you train with, make a lasting impression. Remember his drop dead gorgeous sister also.