Re: Lump on Inner Thigh...
At your age it's not likely to be cancer, but it should be checked out. However, given the activity you've been doing lately, I'd more likely suspect that it might be a boil. That should be seen by a doctor, as they can lance it safely and let it drain, and tell you how to prevent further infection, but it's not a big deal if that's what it is.
Regardless, you should see a doctor about it.