Hi and welcome to Healthcaremagic. Thank you for your query. I am Dr. Rommstein, I understand your concerns and I will try to help you as much as I can. Well, this is unusual sign and if there was no any trauma of infection then you should see doctor and do doppler ultrasound to rule out possible deep vein thrombosis which is manifested with unilateral swelling, pain in calf and lividity of the skin. This may be serious if blood clot travles to heart and lungs so it should be ruled out as soon as possible. I hope I have answered you query. If you have any further questions you can contact us in every time. Kindly regards. Wish you a good health.