Sore throats are always a sign to see doctor. There are a million reasons why. My own doctor has many times told me, sniffles, aches, runny nose, post nasal drip, etc. could be cold, but always says "if you get a sore throat, please come in."
Until a culture is taken, you just don't know. A classmate once had a sore throat and 3 days later was dead from spinal meningitis. Just sayin'.
** ANY ex smoker should always have these things checked out. Even if we are vaping, we have done damage to our mouth, throat, esophagus, lungs when we smoked. These things always NEED to be monitored, esp. if there is something unusual happening! Vaping doesn't mean that everything you did as a smoker is "undone". You will have to monitor forever, really.
In your case, after seeking medical care, I would seek help from the vendor of THAT juice. Find out what the flavoring is, etc. Ask if they have anything w/similar ingredients that you can sample to see if it is the flavoring. Otherwise, you are left out in the dark and/or left never ordering from them again.
To me, this is what having a 'good' relationship with your vendor is all about. If you are a loyal customer and they can't or won't help you find a vape, can't offer any insight, then I would move on. Squirting some flavoring into so nic solution is something anybody can do at home.

If you want more than that, from a "professional", then they should be able to answer those questions.
ASK them if they can mix you the same juice nic/ratio and just leave out "one" flavor. Then see if that helps.
Ask them to help you so that you can continue to be a good customer. It is a win/win situation.
Sorry, but I've reached that point in my vaping journey. I operate under the assumption that juice mixers should know more about vaping than a kitchen table DIYer, and if they don't, then realize that
all you are paying for then is "convenience", ie, having somebody else mix stuff for you. Not knowledgeable professionals.
I don't know any vendor that I deal with who has no concern for me as a person. If they have received orders from me for a while, and know my name, they are willing to help me not do harm to myself and/or customize my vaping experience. And I also appreciate if they are honest, ie. "we don't have the setup for X ratio of VG in our juice line" That's okay, too.....just let me know what I'm dealing with.
If they don't care......well........then they don't see an order again.

People are making a good living off vapers. With that, there should be a strong customer service component but that is just my thinking.