this sucks,,,ive had this happen with tri injections,,,it is strange,,it goes down to the elbow,,,it is usually fine,,,,but this last time got very red, swollen, like a fat persons arm, puffy, red, hot to touch, painful, had to put my arm in a sling could not bend it, couldnt do shrugs, no curls, no back exercises,,,,had to see a doc and it for me was cellulitis,,,google cellulitis and see if thats what you have,,,,it sucks,,,doc put me on doxycycline and 3 days later im finally to the point where i think i can workout,,,,i hate this crap,,,,might wanna see a doc if it gets puffy and you cant bend you arm,,,antibiotics take care of cellulitus pretty quick.