I had the same but bigger, its not a thrombosed vein, its a "lymph vessel" (sclerosing lymphangitis) and I had this for about 2 weeks without doing any exersices but nothing happened, it was still there. One day I tried massage it and the lump was shrinks down and magically disappear. Just try massage it in all direction, circular motion in different pressure - try and find what works for you and vessel will completly disappear