No scale to judge the pot size but I guess 3" or 4" across? 4" should be plenty if you water properly and the tree is already quite small in comparison to the container. Overpotting can sometimes be worse than underpotting so don't upsize too much in one go.
Small containers do not offer much leeway in watering. If that pot is under 3" I'd certainly pot into a larger container soon. My guess is the roots will not have filled that pot yet in which case much of the potting soil may fall away as you transfer the tree. That does not matter as you will not be cutting roots and may even be beneficial as you won't have different soil mix inside and outside of the original root ball. Just transfer as gently as you can, trying to minimize root breakage but all trees can cope with some root loss any time of year.
