Knot in the middle of penis around the urethra

You mean a lump?: Most likely benign. Need more information, such as- has it developed suddenly or over a long time? Is there any pain? Does it affect your urinary sream/ have you had a UTI or std?. Could be a sebaceous or epidermal inclusion cyst, urethral diverticulum, urethral stricture, urethral condyloma etc. Hence need to see a urologist to diagose & treat if necessary.