It most likely went into dormancy from its time outside. It would
probably be best to keep it dormant now until spring as bringing it out
of dormancy would likely stress it very badly. Find a cool but frost
free place, an unheated garage, a cold cellar would be perfect. You
dont need light for it while it is leafless and dormant either. Water
it a bit from time to time just to keep the root ball from drying out
completely. Put it outside again when the threat of frost has passed.