I have a bump on the back of my calf, it's a little bit smaller than a penny. The bump is purple like blood and raised from the skin. There is not bruising around it. Just the bump itself is dark purple. Upon touch if feels like a lump underneath. I do not have any pain associated. I have not bumped or hurt myself recently. It does appear to be a bit larger today. I'm 26 years old. I gave birth 3 months ago to my first child,and I'm on the patch for birth control. I also smoke. Is this a blood clot, or could it be something else?