I am sorry to hear about your medical problems. The pain on extending the arm can be due to
tennis elbow, golfer’s
elbow, tendonitis, bursitis, fracture or nerve compression. First show this to your family doctor. You may also need to see an orthopedic specialist. Meanwhile, apply ice pack, rest arm on sling, and non-steroidal anti-inflammatory such as Aleve or Mobic. Hope this helps. Take care!