Hello~Yes, it does sound stress related. In my teen days, I use to get cold sores on the inside of my lips, man they hurt, I put "Merthiolate tincture on them and it helped. I also avoided things like chocolate and other acid-type foods.
I also agree with the other poster, exercise is great for stress, go out in the nice weather and take a nice walk, it may just help.
Wow, you sound just like me. Whenever I'm stressed, I get a cold sore looking thing on my upper life; always the same spot. It stays for a week or more (never more than 2 weeks) then goes away. It's actually become my "barometer" for stress; I know when this bump pops up it's my body's way of telling me I've got to dial back the stress and take care of myself. Get a LOT of sleep, don't drink alcohol, and try doing something every day that will bleed the stress off of you (meditation, exercise, dancing, anything that helps you feel better that isn't a drink or a drug.)