Suggest Remedy For Itchy Rash With A Head On It On The Upperarm

I'm a 23 year old female and I woke up 2 days ago with a rash on my upper arms. About 4-5 days prior I noticed what I thought was a bug bite but it has become flatter and it appears to have a dark spot in the center. The rash that I have looks like small pimples and I think it may be spreading to my legs. I have done some looking and the only thing that sounds similar is pityriasis rosea. Does this sound like a possiblity? The rash is slightly itchy but that may be in my head as I have been worrying about it since it stated.
Thanks