Hi Puff and welcome
If you've only been vaping a couple of weeks you will probably find that the sore mouth will disappear soon, your body is adjusting to changes in what it's used to. You could try a very low nicotine mix to see if that helps; did your Tank kit have a low nic option? In the meantime, use some glycerine from the chemist (make sure it's 99% or more pure) for your sore throat and later, when you want to make your own mixes, it will come in handy.
Remember to draw slowly and not too hard, it's a little different technique to puffing on an analogue and that will reduce the kick to your throat and help you get the best out of your Tank vaping.
Congrats on a great choice of kit