HELLO THERE. MY COUSIN HURT HIS LEG PLAYING SOCCER FEW MONTHS AGO. HE NEVER TOLD ANYBODY. HE GOT HURT AGAIN IN HIS LEG AND ALL OF THE SUDDEN HE GOT A BIG GROWTH LIKE AN EGG AND IT IS HARD. HIS PARENT SENT HIM FOR AN MRI AND SHOWS HE HAD A BIG MASS BETWEEN MUSCLES . CAN THIS BE DANGEROUS?
It could be a hematoma.  Just want to know whether it is a painful or painless swelling.  I would advise you to get a surgeon opinion. Ideally this growth should be removed.