My Mom Is In A Nursing Home And Pretty Much

My mom is in a nursing home and pretty much not able to move her legs or arms by herself. she is total care. One day, we found her w swelling and bruising on her left inner thigh close to the groin. Nobody admitted that she was injured I.e. fell from bed or something or someone forcibly pulled her thigh. She is a very fragile 87 year old. the doctor taught it can be cellulitis and prescribed her antibiotic. That's ended. But her swelling remained. A Doppler ultrasound ruled out Dvt and X-ray ruled out fracture. Now, all the swelling is gone and no more bruising. But the inner thigh is hard. Like a muscle of a person who works out. What could be the cause of this? Should I be concerned?