Welcome to HCM
We understand your concerns
I went through your problem description. I suggest not to worry more about the problem because it is quite natural. Whenever you stretch your pelvic muscles, the scrotum
always keeps itself shrunk. That is natural.
If a shock
is applied to the area, the muscles gets contracted to absorb the shock and stays contracted for some time to have more blood flow and thereby easing pain etc.
This always happens and mostly you are noticing for the first time. Don;t worry. The pain should also go away in two days. If not, do consult a physician.
Hope this clears your doubts. Available for further clarifications.