I assisted my mother getting up off the floor, she didn't fall, but slid out of her chair. She is 79, her skin is very thin, she showed me where she had torn some skin. But was otherwise unharmed. When I helped her to her feet, and sat her in a chair. I went to get a bandage for the torn skin. When I returned, there what was, what I can only describe as a blood blister, but I know that isn't what it is. When I helped her up she held my hand and i pulled her to her feel by her arms. I bump is the size of a silver dollar, black and blue and a little tender. I have seen something like this in a work place injury before, when someone was pulling very hard on something and had a similar injury. What do you think this is?