What Could Small Cyst In Armpit With Protruded Vein Be?

Okay, about two to three weeks ago, I developed a bump in my left armpit. It grew and I figured it was a cyst of some sort. I asked around on the internet and I found a lot of people who had had it before, teenagers and adults alike. They told me that it goes away in about a week and that it was caused by putting antiperspirant on too soon after a shower. It did shrink away, disappearing after a little more than one week. There s still a small bump where the larger cyst used to be though, and I was supposed to go to a doctor about it. Now, the vein. For a while I had been feeling a slight discomfort in my left armpit whenever I lifted my arm up too high--and I also sleep with my arm up, under my pillow and head, and that would cause me discomfort as well. Yesterday I was pressing my fingers into my underarm and I felt... this vein that kind of protruded at the place where my underarm crease is. I can only feel it when my left arm is lifted up high enough, stretching my armpit. What is this? Now I m afraid to lift my armpit too high because I m afraid I ll snap that vein or something! I hate veins the way some people are creeped out by blood. My mom told me to take some ibuprofen, thinking it s an inflamed vein. I don t see a difference at all.