Some help, please?

I'm a 17-year old girl. Yesterday morning, I found a lump below my right armpit. It didn't pain any, so I thought I would give it a few days time and in case it's still there I'd consult my doctor. However, this morning I was having a slight fever and my right arm hurts when I put my arm bởi the side and also when I tried lifting it high.

I've never had one of these before. It hurts some when I touch it. Does anyone know what this could be?