My 9 year son has small penis like 1 inch is this serious please help me?

Normal: Your son is pre-pubescent. This is normal.

Worth having checked: Maybe normal. Best penile length measurements are stretched penile length by pushing ruler or tape measure down onto pubic bone next to penis ; then measuring to tip of glans. 1 inch would be very small ; in the micropenis range. Large prebubic fat pad can cause a pseudo-micropenis. Best consult pediatric urologist. Possibly a candidate for testosterone as he is srill prepubertal, before too late.