What might cause pain under my thumb nail even if there's no visible injury?

Sometimes your nail can hurt even when you don't see a scratch or bruise. One reason might be retronychia. This is when the nail starts growing in the wrong direction and pushes against the nail bed. It can cause pain and inflammation without a clear injury. Another possibility is a tiny injury to the nail bed that you might not notice. Even small traumas can affect the nail's growth and cause pain. Sometimes, there might be slight bleeding or a small collection of blood under the nail (a mild subungual hematoma) that isn't easy to see. These issues can create discomfort under your thumb nail. It's important to remember that even when nothing looks broken or bruised, our bodies sometimes tell us something isn't right through pain. If the discomfort continues or gets worse, you can start by using a free symptom checker to help identify what might be causing your nail pain. However, it's also a good idea to visit your doctor, who can examine your nail closely, possibly using special tools, and suggest ways to reduce the pain and help your nail heal properly.