I don't believe we have lymph nodes on our groins. We have them under our armpits and close to behind the ears but on our necks. Almost where the tonsils are. It is quite possible that it is a benign cyst. But your doctor should have told you something about it if she found anything wrong with it. What I suggest is having your mom take you to a woman's health clinic, or better yet, a free clinic. And get it checked out. I only suggest this because of the location of the bulge. You didn't particularly specify where the lump was located on your groin, but if it is near your belly button, it is possibly you might have a growth on your uterus, ovaries, or fallopian tubes. The growth could be a benign cyst, or it could even possibly be a tumor. But those are just worst case scenarios. Please have your mother take you as soon as possible.
I have the same problem, along with abdominal pain. I agree with Tsunaamii on this one, you should really get another opinon on this one, because it could be a cyst. There could be something serious.
Now, my abdominal pain is the upper right. It's my liver, specifically, that much my PCP has figured out. I do have lumps, rushes, and sores associated with that disorder.
You should deffinately get checked out again. Before you go in, keep a close log of when you have pain, any bowel/urinary changes, or other weird things that aren't "normal" for your health. Also, log where the spot is exactly, how it changes, and do all of this the same with the abdominal pain.
We do have lymph nodes in the groin. Lymph nodes swell when we are fighting infection or they are blocked. Have you ever had Mono? That can cause the lymph nodes to be swollen for prolonged periods of time.