My Mom Had An Iv In Her Hand For Some

My mom had an iv in her hand for some bone strengthener as part of cancer therapy on Thurs of last week. She woke up today and her arm was sore but now she has bruising, swelling in the arm as well as a hard lump where her vein is where you would draw blood. The iv area is fine. No swelling or discolouring. She saw a walk in doctor and today and he thought it was a clot but she just had an ultra sound and they said it was not a clot but could not tell her what it is or provide her any treatment. Suggestions?