According to WebMD, bruises that feel lumpy, rubbery or spongy happen after an injury causes blood to pool in a certain spot under the skin. These hematomas are considered minor and usually heal over time.
Bruises are a result of broken or ruptured blood vessels. A mild injury to the skin often creates a superficial bruise that spreads out and appears red, blue or purple in color. An abnormal bruise that creates a lump can be caused by being hit with a blunt object, or bumping into an object with force. Though they can be painful and terrible to look at for a while, lumpy bruises are not related to blood clots in any way.
While mild hematomas and contusions typically heal within five days, more serious bruises may take weeks or even months. If you're concerned about a bruise, have a doctor check it. About.com states that some people are more prone to bruising than others. The tendency to bruise easily is a trait that can be passed down through generations. Women bruise much easier than men. Older people are also highly prone to bruising since skin becomes thinner as it ages, making it easier for blood vessels to rupture.