Thanks for the query.
You might have developed furuncle
These are deep bacterial infections.
Treatment is with antibiotics.
The hardness can be due to accumulation of pus.
A photograph would have helped in diagnosing better.
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.