My daughter,who's 15, has a place on the top of her left foot. At first glance, it looks like a knot but its soft to touch. It also has a balloon like affect, the size changes. We first noticed it when she was about 5 or 6, she injured her foot playing, hairline fracture. This knot appeared like a couple weeks afterwards. Recently she hit it on the back of a bus seat, took her to er, they xrayed it, not broken but bruised badly. A week later, the knot reappeared. Is this something that needs my immediate attention?