I have a blood vessel lump in my groin about athe length of the end ogf my thumb really worried?

See a doctor: There are several possibilities it could be a varicose vein if it on the skin , it could be varicocele if it in the scrotal sack , it could be many other things including a normal variation . The only way to know is to see a doctor . You could start with a primary care physician or see a urologist or vein specialist such as a phlebologist.

Ultrasound: Suggest md exam and ultrasound to confirm if vein or something else such as hernia. If soft and compressible likely not enlarged lymph node. Further management dependent on results of ultrasound, but doubt anything to worry about.