About how large is the knot? I saw a similar post about this from another user. I agree that it's possible that it's a swollen lymph node, or even a cyst. If it's a larger knot, it is possible that it's an inguinal or femoral hernia. Definitely look into this to see if it's a possibility. Like the above poster, I also had surgery to correct two hernias, so I would be glad to help out with any questions about them. Mine were not in a dangerous stage, so I did not feel any pain, only a little bit of discomfort during exercise. I was able to do the typical "hernia cough test" and found that when I coughed, the lumps would bulge some. When I laid myself down, they flattened. A hernia may not flatten out if it's strangulated (the tissue poking through is stuck), and this means that it needs to be looked at asap! If the knot is quite small, it's probably something else though. Also, does it feel that it's at the surface of the skin, or a bit deeper in? Hernias are caused by a weakness in the muscle, where tissue bulges out, so these would be a little deeper in.