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 not first thing to think of but may indicate deep vein thrombosis which means that clot is formed inside the big leg vessel. So you need to do Doppler ultrasound to rule this. Vein thrombosis which is manifested with unilateral swelling of the leg, pain in calf and lividity of the skin. Some conditions such as pregnancy, obesity and recent surgery may increase the risk of it. This may be serious if blood clot travels to heart and lungs so it should be ruled out as soon as possible and then appropriate treatment can be started. 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.