Hey bud, I just had this happen to me in late October, and even with that setback I just benched 405 last week for the first time. First off, don't do chest for a month. You won't lose all your gains. Take this time to double down on shoulder presses, tricep extensions, lats, all that. You gotta heal up right or its a never-ending road. Then, mash it. Don't stretch it for a few weeks, just mash. That would be a foam roller, lacrosse ball, anything to break up scar tissue in the area and let blood flow. I mashed mine unbelievably hard and its turned out great.
When you get back into it, use light weights for high reps, not to failure, not a lot of workload. Try to use a shorter than usual range of motion. Then start stretching the area VERY LIGHTLY and week by week stretch it more and more and use a bigger range of motion and more volume.
This last part is the most important. It will hurt when you get back into it. You have to be very honest with yourself regarding good pain vs. bad pain. Too cautious and you'll be nursing it forever. Not cautious enough and it will happen again. Err on the side of too cautious.
In the future, to prevent it, You will need to have a better balance of pushing and pulling movements. I would hazard a guess that your pecs are tight and your shoulders ate internally rotated. Since it's already become a problem, you need to do two pulling reps for every pushing rep you do. Rows, pull ups, rear delt work, facepulls, and pullaparts are your best friends for the next year or so.
Any questions, let me know. Good luck!