After EVLT There's a small bulge or hard knot in a vein on the inner thigh of my treated leg? Normal? (Photo)

After EVLT, a knot or hard cord is commonly felt along the site of the EVLT. This is the vein that was actually lasered. If bulging veins(varicose veins)  were removed at the same time, those sites can sometimes also feel like hard knots due to a little bit of blood underneath the skin (called a hematoma). Sometimes patients can develop phlebitis after an EVLT. This also feels like a hard knot but it is typically also red, sore and tender to touch. This is when a vein becomes irritated and inflamed. When inflammation is created by any of these conditions or procedures, you have the risk of developing post inflammatory hyper pigmentation. This just means something got inflamed and your skin became dark afterwards. the serpentine darkness on your thigh seems like the vein underneath became irritated or inflamed and you are seeing the hyperpigmentation from that. It should get better but it will be important to use sunscreen on that area. As for the hard knot, I have patients sometimes use heat on those areas for several weeks following their procedures. As for compression stockings following a procedure it is variable throughout the world. There are studies that have shown that wearing compression stockings after a venous procedure does not alter the outcome. They are mainly there for comfort and it will help resolve the knots sooner.

This is superficial vein thrombophlebitis of tributary veins of the great saphenous vein.Need to take antiinflammatory products like ibuprofen and place topical creams to reduce the hyperpigmentation (see link below). I also recommend Scler-X

What you describe is very common post EVLT.  The harness pictured seems to be due to the veins clotting post treatment.  This is a result of the laser heating the saphenous veins causing them to contract and the microphlebectomy areas becoming hard from trapped blood.  Wet heat and ibuprofen will help but if these areas hurt you, they can be drained by a small needle puncture under local anesthesia.