Hello,
It can be due to allergic recation or hives. Hives (medically known as urticaria) are red, itchy, raised areas of skin that appear in varying shapes and sizes. They have a tendency to change size rapidly and to move around, disappearing in one place and reappearing in other places, often in a matter of hours.
So please get this possibility evaluated.
Till then, take some antihistaminic like Benadryl and apply some calamine lotion. If the symptoms persist then please get an evaluation done by a dermatologist. you may need topical and oral steroids.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
sounds like you just might be allergic to the medication that you took.
STOP scratching...it releases more histamine, which is what is making the red bump to begin with. the more you scratch, the more spots that will appear. Get something for the rash. Your local pharmacy has it and the Pharmacist will gladly help you. Since I can't SEE the bump, I can not advise you...sorry.