OK, so full non-medical-advice disclaimer here.
That said, I don't have a problem with you informally asking "Does anyone else get this too?"
What I can tell you is that:
1) I vape freebase nic, not nic-salts.
2) I can get some congestion (sinus and 30 years of smoking). I get that upright or lying down though.
And the GERD or other reflux someone mentioned is good to note too.
Now, when I manage to cough up any congestion, it can "sting" in the back of my throat. IDK what that is. Is it the nic accumulating? The PG? A biological reaction accumulating? IDK, but it stings a bit. I have to go get a drink of water, tickles the back of my throat.
I could see that happening when you lay down, as that might help your lungs cough crap up.
I'd consider:
1) Get any medical advice you think warranted, as it could be a COPD indication or infection or some other issue but
2) Consider salt-nic if you're open to it (it's less harsh) and if you're not already using it. Don't over do it though, as it sneaks up on you. You don't get that TH from it.
3) Consider less irritating flavorings or unflavored.
4) Consider less PG and more VG and if you DIY, make sure you add some distilled water into your mix.
5) Try eliminating the nic entirely, and using gum or lozenge or patch for a few days, and vape zero nic and see if it goes away.
6) You're doing it wrong, vape upside down like Batman.
(OK, I'm really making that one up for fun...but....)
All guesses and trying to help.
P.S.
You need to describe "hurts". Lungs or esophagus or throat or what? What type of hurt? Sting, pain like an ulcerated something?