White Mark On Thigh And Back, Hair Growing From It

my son has a small white mark on his thigh, i noticed that mark when he was too small & took it as a birth mark but as he is growing the mark is also increasing slightly, somebody told me it is natural as the leg size is increasing there will be a slight increase in that as well.i shud not relate it to any type of disease- my son is now 7 years old & the mark is almost same older. Further, I noticed a small white mark on his back which was there after when he got himself hurt at the age of 5 i think & there appeared a red line & it pained him for a week later on there appeared a white mark in place of that line. Though these two marks look different in color but I am very worried for this, one thing more, on his back he has hairs black in color on the spot & on his leg the hairs are very few & they seems to be black &1-2 white i am not sure.