Weird cut on toddler's toe

So my son is nearly 18 months old, and I noticed this small calloused patch under his pinky toe the other day but didn't think anything of it. But today while changing his diaper, I noticed he had this weird non-bleeding cut under his other pinky toe. Does anyone know what this is? I plan on calling his doctor but they are closed on weekends so I have to wait until Monday to set up an appointment. Sorry the photo isn't too clear, he is very wiggly!