Thanks for the query.
You might have developed erysipella.
These are deep bacterial infections.
It spreads under the skin as redness
Treatment is with oral antibiotics
Another possibility is drug rash
A photograph would have helped me in differentiating the two.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.