I Have A Ring-shaped Bruise On My Right Arm. I

I have a ring-shaped bruise on my right arm. I dont recall any trauma, I see no sign of a bit.. the dime-sized center actually looks quite normal. But there is a1/2"+ donut shaped area the is fairly dark black and blue around it. I have had some difficulty in both shoulders for several years - and recently tingling in the right arm that I attribute to the pinching of a nerve due to lack of cartiledge in the shoulder. Is this ring a symptom of anything serious?