Sometimes tubers start to sprout when they detect moisture, and they decide it must be spring. Definitely make sure to dry it out if it seems at all damp before storing again.

I've heard arguments both ways for snapping the new sprouts off and for leaving them on... Honestly, I've done both, and if the tuber was healthy and sprouted because of too much moisture and warmth, they do just fine either way.

Sometimes they sprout during dormancy and perfect storage conditions because there is rot inside the tuber, and sprouting is the last-ditch effort to save itself. I've been able to rescue many varieties for my garden by taking cuttings from rotting tubers and growing them on into plants. But it's a bit too early for that... The resulting plant would have a hard time of it surviving for months at end before you could plant it out.

I would check the firmness of every centimeter of the sprouting tuber, and if it gives under your finger at the end, slice the end off with a knife. If its white and beautiful, let it dry for 4-7 days and re-store. If it is brown, gooey or has a ring inside, slice until you have only the crisp white tuber left. Sometimes, you end up with only the neck and sprouts, sometimes you are fortunate and have caught internal rot early enough to save the tuber.