What type on insect bit me? spider?

I live in flagstaff, AZ. I know there is a pretty big spider population up here, and minimal amounts of any other insect, besides moths, and a few big black ants. Yesterday I noticed a spot on the inside of my left knee was itching mildly, but I didn't think anything of it. It eventually went away, and I never noticed anything through my jeans. But today, I was wearing shorts, and I found myself subconsciously scratching the place again, and when I looked at it, I noticed 3 dark pink dots in the shape of a squished triangle, together no bigger than a nickle. The bumps are barely raised, they are rather puffy from being scratched so much, and one has a bit of a businesslike red streak on it. It hurts to the touch, not like a bruise, but more like a cut. It still itches mildly, but nothing that will drive me crazy. Any idea what this could be? I'm kind of freaking out, cause I have this huge thing about spiders. they freak me out.