My son is 8 in march. i have noticed that the head of his penis is blue. he is not circumcised but his skin has retracted. no pain, no burning urine.

Difficult to assess: The penile glans or head is darker in color than the rest of the skin/shaft. That could be what you see. However, when a kid is not circumcised, the foreskin can slip down & act like a tourniquet, cutting some of the blood supply to the glans. If it slips over the top of the glans without difficulty it is not an issue. If the foreskin forms a tight ring below the glans he needs to be seen.