I'd agree that it's likely condensation from the
eliquid passing through your nose (unless you are also noticing/tasting e-liquid as you inhale into your mouth, as well, in which case your coil type and wattage may need some attention and adjustment to stop it from spitting and popping which can result in a mouthful of e-liquid, which doesn't seem to be the case here.
If you don't enjoy it, you can just not exhale nasally. The sinuses are good at absorbing nicotine however.... So it can be a bit of a tradeoff. I don't get moisture when I exhale though my nose but if I did I would likely halt the process. I am a low wattage, high nic vaper however, so my "puffs" are likely different than yours. But, it's nothing really to worry about other than your personal preference with the matter.
Anna