Lump on fore arm from elbowing heavy punching bag. serious?

i just got a heavy bag like a month ago cause i like to keep busy with doing things to stay in shape, an i know the bag wouldve been good for cardio. ive been steadily gettin more better with my hits an "combo's" lately cause ive been at it like every second day but last night i had a good night, an after a few good elbows i noticed my fore arm on the outside halfway between my wrist an elbow had a big egg shape on it swollen hard. i stopped an i figured it was just a charlie horse but it didnt go away. it doesnt hurt at all, my arm is just really tired. i iced it before bed an kept it elevated, an it still is sticking out today but just like an inch out with no pain still.. is it just a charlie horse or could i of some how got a hair line fracture?