I had to ask my doctor about it who asked me to do ultrasound test as she suspected it's a deep vein thrombosis(DVT) or blood clotting. Thanks God the result showed otherwise. It's a swollen muscle probably due to exhaustion. The dark spots I believe frightened my doctor. She asked me to reduce my blood thinner intake and repeat the INR test in two weeks.
Thanks God it's not DVT. Diagnosis after all the tests is myositis, inflammation of the muscle probably due the Atorvastatin I'm taking as an anti-cholesterol. My physician changed it to Rotuvastatin as my cholesterol level was higher than normal.