Those are really good questions, and the answer to both is: not necessarily.
Injuries are rarely ever caused by one big trauma. What I mean is, while it’s certainly possible to slip a disc trying to carry a piano up a flight of stairs, it’s usually the case that lots of little micro-traumas build up over time. The sort of pain you’re describing is a fairly solid indicator of that happening.
Your daily life contributes hugely to this kind of thing. Do you sit at a desk all day? If so, then your shoulders will be locked into internal rotation for way more of your day than they are in external rotation. That’s the sort of shit that adds up over time. It’s usually compounded by the fact that guys do way more chest work than back work (not saying you do, just that guys often do) so even more internal rotation and so on and so on. And it’s not just sitting at a desk that fucks you. Really, any job that puts you into a certain posture for a large part of the day is doing to lead to some kind of postural deficit over time. Just how it is. You can combat that shit in the gym but if the other 23 hours a day are causing you problems, that one hour in the gym isn’t going to do much to help!
Obviously lifting with good form will minimise the damage but the thing that people forget is that all reps, even those done with perfect form, cause wear and tear on joints. It’s like anything - you can only use it so much before it starts to wear away. Good form will stop that from happening for a very long time though! At least, it should…
So look after your shoulders. Do lots of mobility stuff, external rotation stuff, etc., but also make sure you are training the shit out of your upper back, doing much more horizontal pulling than you are vertical (so think rows, face pulls, etc rather than pulldowns).
You might want to get away from barbell pressing for a while. Try pressing with dumbbells using a neutral grip (like you were holding a cup of tea (although don’t lift your pinky)). That gives the tendons in your shoulders more room to breathe.
SMR, massage, etc like the poster above mentioned are great but they only treat the symptom, not the cause. The goal should be to work out why you have the pain in the first place and eliminate the cause, rather than just doing your best to alleviate the symptoms.
Best of luck with it!