Probably simple dehydration combined with the factor that your throat is still healing from the tobacco pounding, and will be sensitive for a while. Drink lots and keep to careful draws for a couple of weeks and it'll probably go away, it did for me.
It could be that you only have a fixed voltage battery and a 1.8 ohm coil. When I started, and had the sore throat, it helped me to put in a 2.5 coil for the first couple of weeks.
If it gets worse, or continues past a few weeks you may not be a fan of PG. I read that some peeps bodies don't like it. There are VG heavy options for you if this is the case, but I think the peeps that can't handle PG are very much the minority, so don't jump to any conclusions too quickly.