Could this be a skin infection?

[afjstdfyas]

I noticed this  http://imgur.com/aIH58uV  on my boyfriend (21M) tonight. It's on his upper-middle back... he didn't see it due to the location, and he thought it was a swollen pimple because the area is raised. I drew a circle around it to monitor if it grows and put Neosporin on it. He is prone to eczema, but it usually just looks like hives and is itchy when he gets it. He is saying this is not itchy or painful, and he's not having any other symptoms, so he's not worried, but I'm concerned about a staph infection or something of that sort. Any ideas what it could be? Should he see a doctor and how soon is it okay to wait and monitor? Thank you!