I think I might have fucked up.

A few days ago I started lifting again after a long break (I was trying to run more to get my 1.5 mile time down) and everything seemed alright, and as per usual I was slightly sore. But that was 4 days ago, and I can't fully extend my arms all the way without quite a large amount of pain (not the normal lactic acid build up kind of pain.) I've tried stretching to let any lactic acid move around and do its thing, but still no luck.

Did I over do my workout? If so, how can I tell if I did any serious damage? I'm probably just a little paranoid, but it doesn't hurt to be safe.

Pic unrelated, its just an attention grabber.