I've been lifting for a few years, but only recently did I start getting serious about it. However, two weeks ago I was attempting 10 deadlift reps at 225, when on the third rep I felt something twinge/pain in my arm. More accurately, the pain was in the front 'edge' of my left armpit that connects my pec to my shoulder/bicep. (There's probably a better name for this, but I don't know.)
I stopped the set, and took one week off from the deadlift. Last week I tried deadlifting at 135 and it still hurts, but not as bad. The 225 I was lifting at shouldn't been a problem, since my 5 rep max is 255. (I'm 5'10" and weigh 165)
I'm not sure how long I should be resting, or how else to heal this injury. Was there a possible form problem that caused this -- I'd like to fix it if possible.