J.D.
does she have dry skin?
It might be something you can look into and try to put some lotions on her skin to see if that helps.
If not she might be self harming if shes picking and giving herself marks on that note I would contact a child psychologist and have them maybe observe her.
I would also try to get it on video so if you do decide to take her to a doctor if she doesnt do it for them then you have proof that she is indeed harming herself.