Assuming you cleaned it before putting it away:
Prime the atty with ~6-7 drops of the liquid you intend to use. If it is still giving you a burnt taste, add another couple of drops. If it is still giving you a burnt taste, then you probably scorched the wick before and
you'll need to de-wick it. It's easy and can be done with a toothpick in about 30 seconds. I do not necessarily recommend debridging because that process is a bit more complex and can result in a leaking atty. I do occasionally debridge an atty, but for your purposes and the fact you only have the one atty, I think you should avoid it.
As to changing flavors: For a lot of mellower flavors or similar flavors, just blowing the excess juice out of the atty is usually enough to get rid of the previous flavor so you can move on to the next. For stronger flavors or when switching between very dissimilar flavors, you might need to give you atty a quick bath in PGA or vodka and blow it out. After a vodka bath and blow out, I shake my attys sort of like a thermometer to remove any residual alcohol before priming and
vaping again.
Hope that helps!