I Have Semi Rigid Lump That Developed On The Inside

I have semi rigid lump that developed on the inside of my right thigh it feel somewhat movable and has softened a bit. It is not painful, just a bit uncomofrtable. it is maybe the size of my thumb. I have recently been exercising consistantanly (the last 9 months) and have lost well over 120 LBS. Most of what I read seems to indicate it is in an infection.