I am a twenty year old female. This morning I woke up for work and when put my shirt on I notice my armpit was sore, I thought maybe it was a zit an took a quick glance and no red mark was there. So I continued on with my morning but it still hurt, so i felt it, when I felt it I noticed under my skin was a lump about half the size of a grape that was tender, but not tender like a zit forming, like painful :( I've been told it could be a water cyst under my skin by a friend, or a swollen gland, could this be true?
From your description it sounds to me like you have an inflamed gland. Armpit area, besides having pores and hair that are usually responsible for zits, also has sweat glands relatively close under skin. When they are working properly, you can't feel them, but when they get inflamed they feel like an under skin zit, maybe bigger in size. This inflammation sometimes just goes down on its own - like it appeared over night it can go down in a few days without any treatment. However, if you continue having problems, or the swelling and pain get worse, you should see your physician because you might need antibiotics or steroid topical cream to bring the inflammation down,
Wish you all the best,