Hi, Several Months Ago, I Noticed What I Thought Was

Hi, several months ago, I noticed what I thought was an ingrown hair under my arm. I scratched it, and it came out. It was really small, and I didn't think anything else of it until a few days ago.
I was putting on deodorant (not anti-perspirant) and noticed the same area is indented, and a little reddened, and slightly itchy.
Any ideas what this could be? My doctor just says, oh, an itch? Here's some hydrocortisone cream.