I Had Cortisone Injections In Both My Knee Joint Muscles

I had cortisone injections in both my knee joint muscles right by the bone and my knees started burning the night after the injections. Now I itch everywhere and feel heat everywhere. The doc said I could take some pain meds and antiinflammatories bc it could really hurt. I can only take pain meds due to autoimmune conditions. I am on the second morning and feel heat and itchy all over. I took a Benadryl this morning just now but should I be worried? I was very careful with my meds.