Hi... My Boyfriend Got Bit Or Stung By Some Sort

Hi... my boyfriend got bit or stung by some sort of bug while riding four wheelers in bitely michigan and it looked like a bee sting at first so we put baking soda and water on it. The swelling went down but now it is really itchy and feels like a bruise. There is no mark other than it being really red on his whole inner thigh but that may be from scratching it. We tried cortisone 10 cream but that didn't help much and benadryl extra strength cream