PG !!!!
It's definitely the pg. Rough isn't it. Some people are more sensitive than others. And plenty of people know about this particular problem. You will wind up with a sore throat and start thinking you'd got a cold coming on. You just have to increase the "VG" ratio in your juice. Or get vg e liquids in future. You'll find most vendors sell high ratio pg solutions. You'll have to do some searching to find a vendor that gives various options. I don't use pg at all. I use 100% Vegetable Glycerine, smooth as silk !.
Trouble with VG is it lacks flavour and throat hit. As it stands i've tried about 2 dozen flavours, all in vg, and only 4 of them have worked out. The nicotine level really doesn't seem to matter as far as throat hit is concerned with vg, meaning it doesn't change the intensity of the throat hit, not in my experience anyway. It mainly comes down to the flavour your vaping. So just buy to try. Get a few 5 mil bottles of various flavours in vg and start working your way through them. You'll find some that work for you eventually. For me menthol works really well, i mean really well. Don't use it much anymore though because i found other flavours that i prefer much, much more. "banana nut bread" another good one in vg. "Cinnamon and sour apple" in vg is great, very strong taste, too strong for some. "Old holborn"(natural extract") in vg, good throat hit. Oh and "honey nut" in vg, again, good throat hit. Always going to be about the flavours. Believe me, a lot of them simply don't work.