Q. Two days ago, you diagnosed a 54-year-old woman with atrial fibrillation and started treating her with warfarin 10 mg/day. Today, she returns to the emergency department with a large, painful skin lesion on the dorsum of her right forearm, extending from elbow to wrist. She noticed the lesion a few hours ago. Her temperature is 37.4 degrees Celsius (99.32 degrees Fahrenheit), pulse 91/min and irregularly irregular, respirations 12/min, and blood pressure 127/76 mmHg. The skin lesion is ecchymotic, slightly tender, and elevated, with sharp margins. It is slightly warmer than the surrounding tissue. Her lab tests show normal platelet count, PT 14 sec and aPTT 38 sec, and a low protein C level. What is the best plan for her skin lesion?