What Causes Swelling And Discoloration Of Leg After Taking Paracetamol?

My mother is aged 81 and last Saturday developed a slight fever which was controlled by OTC paracetamol. On Sunday, her right leg (a small portion on the front, between the ankle and the knee) was swollen and a bit discolored, she was in pain and could not stand on it. When we tested her blood sugar, it was 260. What should we do?