I got two shots of degarelix one side ok the other hard as a rock hurt and red.. Why?

Known side effect. This can happen with the first dose. It will go away but can be very painful. Sometimes doing the injection as a deep subcutaneous can help. Hopefully the benefit from dropping your psa fast will be worth it.
Possibilities. Most likely cause: bleeding under the skin at the site. Since the other side is ok, it's probably not a reaction to the medicine itself. A third unlikely possibility is infection. If you have fever or it's not improving, please have it looked at.