My 3 year old son has a thick vein at the base of the ...

Hello, I have a 3 year old son and I noticed that at the base of the penis, at the top there is a thick vein bent in U. He recently did a frenuloplasty and at the moment of exercise for the exposure of the glans, I realize that this vein looks like a ball, swollen. He has normal erections. Is this vein normal?