What Causes Swollen Lymph Node On Hip Flexor?

At least a week ago I noticed what seems to be a swollen lymph node on my left hip flexor. I am not certain exactly when it arose, but I first noticed it shortly after completing my first heavy leg workout in at least a year. I waited about a week before doing another leg workout, and in that week, I think it may have gotten smaller, but it wasn t really very large to begin with. Anyhow, today I worked out my list body again, and it seems to be irritated again (still not sure if it has changed in size). It is slightly sensitive to the touch, and other than the expected soreness from a workout, I don t really notice it. I am a little concerned as I have never experienced anything like this. I eat healthy, and I am a relatively active person, I just want to be sure I m not going to cause any additional complications and hurt myself. Could this simply be caused by over-doing it in the gym? Or potentially something more serious? I am going to start taking some Advil in the mean time. Any insight would be greatly appreciated.