Thank you for the query.
First of all some good news for you. Most of such lumps are benign lesions and not a cancer for sure.
Yes, it can be a hematoma
caused by the trauma in January (sometimes blood collection can stay in the tissues for years). It can be also a cyst or lipoma
). All mentioned types of lumps are benign and can be easily diagnosed with an ultrasound
Hematoma should be drained with small incision. Cyst or lipoma can be removed and send for histopathology to make sure no cancer is present.
Hope this will help.