I may be worrying about nothing but I've noted that it takes ages for my ds's (4 years old) skin to heal.
When he was 9 months old he nicked the skin near the eye - it took a year for the scar to go. Then last summer he got a carpet friction burn the size of a two pence piece playing with his friend - it's only just faded this summer.
In early June he got chicken pox - he didn't scratch the spots at all but where he had the spots are very dark brown marks still.
Does this healing (or non)healing time sound normal in your experience?
Otherwise he's in great health.