Yesterday while at work I noticed out of the blue a small swollen knot the size of a marble on my left arm, in the middle between my wrist and elbow...on the same side as the back of my hand....it did not hurt..but I could roll it around and it was very scary to both myself and my coworkers...they suggested that I go to the emergency room, as one employee believed it was a blood clot in my vein...about 20 minutes later...it went down completely...today the skin there looks like a super super light bruise....should I seek a doctor for examination....not sure if I should be concerned....I am 39 years old and female