Based on the symptoms you described, such as a vein feeling constricted and numbness up to your thigh, it is important to seek medical attention from a doctor. These symptoms could potentially be related to a condition called phlebitis, where a blood clot in a vein of your leg can cause a sensation of tightness. If left untreated, phlebitis can worsen and lead to more serious complications like a pulmonary embolism or a stroke. It is essential to consult a healthcare professional to properly diagnose and treat the issue.