Rashes With Small Scabs On Upper Back To Chest With Patches, Burning And Tingling Sensation. No Itching. History Of Going To Public Swimming Park. Infection?

I have a skin rash now for a week. Now i have small scabs in then. The rash started in my upper back and went along my ribs to my chest only on the left side. There are dozens of patches all along with scores of heads in each patch. my skin doesnt itch but the whole area fells like it got burnt. I still feel a tingling sensation in the back at one point which is at the peak of my shoulder blade nearly impossible to reach with my hands. I put 1% hydrocortisone for three days. But that burnt feeling is still bothering me. Any ideas? what it could be and what to do about it. BTW i went into a public swiming park and might have caught something there.