Hello and thankyou for approaching DoctorSpring with your query.
Please can you give me more details so that I can give you an informed opinion.
We will first need to rule out any cardiac cause of your chest pain
1) Do you have any sweating associated with the chest pain?
2)Was there any nausea or vomiting?
3)Is the pain radiating to you shoulder neck, jaw or arm?
4)Did you have any transient loss of conciousness (syncope)?
5) When did the rash begin? Can you describe what the rash looks like? Is it a cluster of blister? is it all over your chest or on one side of your chest?

Since you have developed a rash too, it is most likely a viral infection and there is no need to rush to the ER
But if your pain gets worse and is constant, radiates to the shoulder, jaw, neck, or you start sweating and feel restless please go to the Emergency Room immediately to rule out a cardiac cause.

Please reply to my questions as a follow up so that I can give you a better opinion
.
Thankyou