ARS has no specific symptoms.
Actually, as far as I know from my doctor, ARS should have these symtoms:
- fever
- muscle aches (specially abdominal and legs muscles)
- swollen lymph nodes (not only one)
- rash (back and chest)
Don't know what exactly is this information, but almost 100% ARS cannot include only what you described. Of course, this doesn't mean anything and only a test is conclusive.
a small patch on left arm only is NOT an ars rash !
I don't think ARS can appear after 1 week. And as far as I read should be more than one symptom.