I Have A Small Raised (bite?) Maybe Which Is Red,

I have a small raised (bite?) maybe which is red, raised and in a straight line on the right side of my lower back. I noticed it last week and it was just a little itchy and I dismissed it as maybe a small spider bite. Sunday morning I noticed tenderness to the touch on my lower back, but my side and under the right breast/rib cage area. Monday the tenderness is still in the general lower back area but also showed up on the inner right arm. It feels better temporarily with coolness such has cold hands. It is only on my right side, not the left at all, nor lower body.