My son had weird rashes like that and they did not blanch when we pressed on them. It had something to do with his 6mp and his WBC being too low. Similar things happen with leukemia when not taking meds. As long as you don't have a fever, it isn't hot, painful or spreading I don't think it is worrisome. When my son had his, they did order blood tests to check for clotting issues and his WBC, which was really low. Once his dose was changed it stopped happening. If it were my son I would probably call and report it to the nurse to see if they wanted to take a look, but I am a nervous nelly!!
Hope is nothing and goes away quickly for you.