Based on the information it seem like a
1) "PENILE FRACTURE"
------------- OR -----------------------
2) "HEMATOMA" due to blunt trauma
Here is some information both along with advice
*** PENILE FRACTURE :- A popping or cracking sound, significant pain, immediate flaccidity, and skin hematoma of various sizes are commonly associated with the event.
*** BLUNT TRAUMA - can lead to a collection of blood pooling inside the organ known as "hematoma", it may not be visible by naked eyes but may be hidden deeply ( the shock
wave can create an tiny blood vessels to rupture leading a loss on blood internally in the organ but the cover of the organ will mostly enclosed it so it will not come out but will stay their) eventually it will be healed by absorption and macrophages(blood cell) will engulf the hardened dark blood but will take a long time to regress
########"CONSULT SURGEON AS SOON AS POSSIBLE "###############
1) Penile fracture is a medical emergency, and emergency surgical repair is the usual treatment
2) Delay in seeking treatment increases the complication rate ,
3) If not taken treatment in time may result in "ERECTION PROBLEMS"
Following is mostly they will do.
1) will do the ultrasound
2) fix it with surgery.
Hope it helps.