hi doctor!

Iam a 26 yrs old female..few months ago I started feeling needle like pain in my right armpit and it went by itself..after that whenever it comes it stronger.A week ago I dicovered a tiny bump in my armpit .it looks like a pink pimple but when i squeaze it its very hard and i noticed a certain type of smell from my fingers after squeazing it.no discharge comes out and its not painful.can u plz tell me what it is?