Keep calm and don’t panic.
Although it’s not as big of a deal as it was in, say, Mass Effect, you still have the capacity to import your save from The Witcher 2 into The Witcher 3, which brings over all your decisions made in that game, and changes the world accordingly.
This can only be done on PC – neither of the two consoles are compatible with their predecessors, and The Witcher 2 was never even out on PS3 anyway – but it can be tough to know exactly how to do it. In fact, at the start of The Witcher 3, you might find you weren’t even prompted to import you save at all.
Thankfully, Polygon has written up a handy guide to help you deal with this situation. As they point out, if this happens, it’s likely that your save games are not in the right place. The Witcher 3expects that your save games live in “:\Users\[username]\My Documents\Witcher 2\gamesaves”; unfortunately, if you ever enabled Steam Cloud saves, they will be in “:\Program Files(x86)\Steam\userdata\[userid]\20920\remote” instead. Just move them over to the expected directory, and you should be ready to resume your adventures on The Continent.