Hello everyone! Girls, I have a question: we've noticed some cracks un…

Hello everyone! Girls, I have a question: we've noticed some cracks under my child's fingers (I've attached a photo). The child approaches, using gestures and sounds to indicate that it hurts. There are sores under the thumbs and a few spots under the little fingers. The pediatrician told us it seems the child has been rubbing them. Although, I find it hard to believe that he could have rubbed them so much, especially in those places. My son's fingers are chubby. Has anyone encountered something similar? How did you treat it? What could it be?