Okay Okay people, when I said doctors I meant someone qualified enough to confirm if youi need more than rest and that something isn't broken, ripped, or dislocated :p
I'll admit that GPs often arn't much good beyond the A&E and that bone is sticking out stage. But not always, I had a ligment problem in my foot, went to my doctor, he knew exactly what it was, printed me off 5 pages of info and some excersies to do, problem sorted :D
I'm up to feet on windowsill level of overhead press, and I agree it's main benifit is it requires no equipment, esecially when starting off with hands on something like a chair or low bench, that's pretty safe, but once you start getting upside down, it gets a bit weird. Maybe it's time to start scanning freecycle for a barbell, then I can add weights to my squat too :D
I'm not a huge fan of head stands at the best of times as there is always a tendency for them to cause some compression in the neck, especially if your alignment is poor,
If you want to work with handstands spend some time on the crow stand and crane stand (like a crow stand with straight arms), try to keep the hips high and build the shoulder strength up over time.
All inverted work has some danger associated with it so do proceed slowly and avoid training to failure.
Go see an orthopedic doctor/surgeon. I hurt my shoulder 8 month's ago. I thought for the first few weeks it would get better. It did a little but I still did not have full range of motion. Long story short, I had a fully torn rotator cuff!! MRI, sonogram confirmed. Had surgery 5 days later. Now 8 month's on, no pain but almost have my full ROM. Doc said it would be a year before it was right again... he was right. Don't take chances and get checked out!!
It is the "pop" sound you heard that makes me think hard.