Low grade fever and small rash appearing on arm of 5yr old?

My son (5yrs) has a low grade fever (highest was 100). He has been complaining of a head ache in the front part (sinus area) of his head for a couple days. He also sounds congested. Over the last hour he has started to develop a small circular rash on his forearm. One small red bump and then 15 minute later 8 small red bumps. He is up to date on all his immunizations including the one for chicken pox. We do not have heath insurance so I came here for help. My mother in law says to give it a bit of time before I run to a doctor. I'm worried. This is my 3rd of 4 kids so I'm not new to this kind of stuff. I use to be able to run right to the doctor when we had health insurance. Don't really have the $160 for an office visit to be told they can do nothing, it's a virus. I've been giving him Advil for the fever. Fever started at @ 6pm yesterday so it's only been 18 hours.