German shepherd skin issue please help

Question

back side  

back and tail   It started 2days ago and It's looking pretty painful and I have no clue what is happening if you could help I would greatly appreciate it thanks

Answer
This could be a "hot spot." When anything itches a dog, they try and scratch it, often breaking the skin.  The skin weeps out serum which is irritating.  So the dog itches, scratches and bites creating more trauma.  The best thing to do is to get all of the hair away from this area by shaving it off and then keeping the area clean.  Your vet may want give a shot of cortisone to stop the itching and some antibiotics to treat any infection.