There is swelling, pain in the area of the clot, redness as the primary indicators. There is often fever that comes with it, and if it is far along enough, there is loss of blood flow to the foot and lower leg, which will make the foot cold. You need to go to the doctor if you think there is the slightest chance that you have one. If a tiny piece of a clot breaks off, it can get into the lungs, or the heart, and the brain, you would be in big trouble. Please don't mess around with this. Hope this helps, good luck to you.