How To Cure Large Bumps And Swelling Under The Left Lower Arm?

i am a fifteen year old athlete, and i play softball. about three weeks ago i got hit with a pitch in my lower left arm, in the same area about two or three times in one game. the area swelled and bruised for about a week and after the bruise went away, a lump formed on my arm. if you slide your hand across my arm, there are about two or three large bumps under my skin. the pain goes through the bumps and up into my hand and wrist. do you know what these lumps are and if they will go away?