Ugh, sucks man. I injured my shoulder about 3 weeks ago during a flat barbell bench press. I try to stick to good form, and I somehow injured it doing relatively light weight (225 lb, my 1RM is 315).
It wasn't an instantaneous pain, but rather a dull pain that occurred after the 225lb set and slowly got worse and worse throughout the day.
So I took it easy for about 3 weeks and worked around the shoulder and did anything that didn't irritate it. So I did legs, abs, and back (rowing motions seemed fine, I just cut back on the deadlifts). After 3 weeks, absolutely no pain, decided to do a chest exercise today and give it a shot. I started out light, and then ended up eventually re-injuring it during a set of incline dumbbell presses.
So now I am probably going to go to the doctor and work around it for much more than 3 weeks this time. It hurts from only specific ranges of motion. It hurts from pushing movements and from front lateral raises especially. Side lateral raises don't hurt. The worst pain occurs if I put my shoulder in a position reminiscent of when you do a lat spread.
On the bright side, my pitiful squat is shooting up like mad from all the extra leg days. I am still a beginner and this is my first injury. I am really impatient and want to get back into it. I was always obese growing up. I peaked out at 345 pounds in January of 2013. By February 2014, I was down to 181 lb. I started to bulk and started getting all kinds of gains. I am now a relatively lean 205 lb. Working on cutting to 190 lb. Never being this fit before in my life makes it really hard for me to step back and take it easy for a bit.