Hello and welcome to HCM, Development of lump after a history of trauma is probably a soft tissue swelling. Hematoma or collection of blood is common after trauma. Internal bleeding in soft tissues leads to accumulation of blood thus hematoma formation. Usually hematomas clear away after few days however, persistence of hematoma can be due to organization or growth of fibrous tissue into it. Hot fomentation should be given to the site. If the lump / swelling clears away with hot fomentation nothing more needs to be done. If the hematoma still persists after hot fomentation, then you need to consult your primary healthcare provider for clinical assessment and thus management. Thanks and take care Dr Shailja Puri