I Took My Son Drs Yesterday With A Flat Rash

I took my son drs yesterday with a flat rash all over his arms legs and stomach. They said suspected viral infection or mild case of chicken pox. When i got home i noticed a blister on his foot. It has a dot in the middle. To me it looks more like a bite or sting im just wondering if you know what this could be. As i know chicken pox start on face and a few blisters not just one