Tweetnever tried prop, but from what i hear it hurts, my first and only bicep shot bruised over, and then i found spot injections dont really produce any localized muscle (or we would all do it). However my delt did the same thing, got swollen and the red slowly made its way down my arm, I dont think i went deep enough, or for some reason my body had a reaction to it.
You will be okay in a few days, it took my shoulder a full week to get to normal, Dont worry to much about it unless the pain gets continually worse instead of better, then it might be an infection.