Small, clustered, raised rash appeared after tanning in a tanning bed?

I tanned last summer in a tanning bed and never got a rash or anything. I just started tanning again, and after tanning the 2nd time, a small rash appeared on my chest, in between my breasts, but actually just below the cleavage. it is small and clustered in that area, but is raised and red, and also itchy (kind of prickly feeling). I know it is not caused by my lotion because i've been using the same lotion for the past two years and never had a problem. It's not the cleaner they use on the beds either, because my chest never touches the bed at all, and i have no rash anywhere else. I have had this rash for a week, i stopped tanning for a while but it didn't go away so i started tanning again, it gets puffier after tanning but does not spread or anything. Does anyone know what this could be? And possibly how to get rid of it? I'm trying to avoid a doctor visit unless i really have to go because i don't have insurance. I think it might be a heat rash but i dont know how to get rid of it. Any idea of what it is and how i can get rid of it?