According to your description (“small open sore that looks like he has been scraped on the head of his penis every now and then after intercourse”) he might have had some erosions on the penis’s head. Erosions can be due to friction if there isn’t enough vaginal fluid to make the sexual intercourse smoother. It doesn’t seem likely to me that the uncircumcised condition can cause erosions on the penis’s head. He can consult his primary health provider and a dermatovenerologist, if necessary.