Can you sue the precicnt?

You do not say what connection the rash has with being in jail except as to time. Numerous pre-existing factors could have caused the rash; unless you have a Dr. to state what it was, I doubt you can show any connection to the police. They can release you without your seeing a judge as long as they do not hold you beyond the tie you are supposed to see a judge. I do not know what state you are in so can not comment on how long they could hold you without charging you with a crime.

I doubt it. You'd have to show that this was their doing, and that they did it to you on purpose. Rashes can come and go with very little predictability.