What Is The Treatment For Sinus Infection And Itchy Hives?

Hi I'm 52 years old and recently had a sinus infection and was prescibed amoxillin. I forgot to take it one day and the next day I broke out in red itchy hives mostly on my torso, but some on my face, arms and legs. They have continued for a couple of days and are bright red with a small white pin size pimple or something in the middle.