Explain what you mean by "overstretching it" during the top of the lift. You should press with shoulder blades back and basic shoulder girdle in a fixed position. Press until your arms reach full extension, and not move your shoulder girdle. Don't rotate your shoulders up to get that last inch. That's what puts you in a vulnerable position and where a lot of injuries occur.
Probably a rotator cuff. If it is a constant pain, you should lay low. Do a search and find numerous threads of people hurting their shoulders and continuing to lift and it getting worse. By doing more exercises that are stressfull to the joint, if not done properly, it's just going to keep giving you problems. And I'm sure like everyone here, since you are on cycle, you were probably pushing it a bit more than usual.
IMO, the decision you have to make is:
1)Am I going to be a tough guy and finish my cycle hell or high water and deal with the shoulder pain, get some pain meds, have it bother you for a lonnnnnngggggg time, or
2)Am I going to use my head, quit pushing it, maybe see a shoulder specialist so that my shoulder isn't screwed for the majority of my life, and figure out exactly what went wrong and how to not do it again.
Been there done that with hurt rotator when I was young and didn't know much about form and technique. Not saying yours was wrong, but you are asking if it is something you should be worried about. It didn't heal completely, my GP I went to was a fat lazy slob that suggested I shouldn't work out so much, so he wouldn't refer me to a specialist. I learned better form, learned how to train around it so I didn't make it any worse once I could start really using it. Now, I am somewhat of a form Nazi because I see so many with crappy form. I won't call you out in the gym or anything, but anyone I am working with I make sure they have good form so they don't get hurt.
My suggestion, try to salvage what you can of your cycle, lay off shoulders, dips, any chest exercises that aggravate it. Get it checked out. Learn the lesson you are supposed to from all this, and do it again better once you are healed up properly.
If you aren't getting payed or making a living from your lifting ability or your physique, it's not worth overdoing it and not getting an injury checked and properly healed. If you do enough damage that it's not just your lifting that's affected, but now your job is affected to because you can no longer perform it due to a stupid accident, was it worth finishing the last couple weeks of any cycle that you may be doing?
And yes, people say a shoulder pain is normal or pretty minor, and that alot of lifters have them, they just suck it up and deal with it. Well, you don't have to just suck it up, it's not worth being in pain for a long time or rest of your life because your ego was too big.
Sorry for the rant, just my opinion.