Had a painful pop in my shoulder while playing basketball and reaching out for a rebound & couldn't move it for a minute or 2. any ideas?

Likely muscular injury: From what you mentioned this is likely to be the cause You need initially to rest it and take some simple pain killers. Keep moving the shoulder as pain allows See your doctor if symptoms continue despite treatment.

Labral-instability: At your age, this sounds like a brief episode of instability that occurs when the ball/humeral head comes out of the socket/glenoid very briefly and then relocates itself. Concurrently or alternatively, a cartilage/labral tear can look and sound like this as well. If I can help, then join my care team at www.healthtap.com/dr-clarkeholmes