More like a mucous cyst, though rare on the upper lip.
It seems to me like it's a cold sore/fever blister, whichever you would like to call it. I have had them since I was little, the whole time from the first tingle to it being healed is usually about a week for me. It will flare up into a blister, then it will pop(on it's own, do not try to pop it!), it will crust, and slowly start healing. They are painful and embarrassing. Mine get quite a bit bigger than what yours looks like. I usually get them twice a year, having a fever, extreme heat/cold or stress can trigger them, alcohol seems to be a big trigger for me, which makes since because your body temperature rises when you consume alcohol.
Knock on wood I have only had one small one in the past two years and it was at the beginning of my pregnancy(I'm sure my hormones and all the crazy changes my body was going through is responsible for that). I use Abreva, apply it several times a day. Burt's Bees use to make this Medicated chapstick that i wore constantly, the whole time I used that I never got a fever blister(Even in the uses it said to treat cold sores/fever blisters). Go figure they do not sell it anymore, I can't find it ANYWHERE!! :/
Also, once you have that in your body it is always there, it just lays dormant.