Oh, don't worry too much, a few of us have noticed similar things with our little ones at that age and it can feel quite alarming when you first spot it. It could be something simple like the nail getting caught or a bit of dryness, but since it is on a young child, it would be good to bring your LO to the PD just to get it properly checked out. Better to have peace of mind than to wonder, right? The PD can take a quick look and let you know if anything needs attention.