A high percentage of skin lumps are not cancerous, according to University of Florida Health. Skin swelling and lumps can be caused by several factors, including trauma and infection.
Lumps that develop abruptly over the course of 24 to 48 hours are commonly caused by an infection or injury. A lump under the skin could be a swollen lymph node, wart, cyst or lipoma, as reported by University of Florida Health. Noticeable and unexplained changes in the skin, such as changes in the color or size of a mole, should be evaluated by a medical professional, as stated by WebMD.