I would pinch out the top that has dried out and you should get more growth lower down the central stem. They are not usually too worried about being pot bound but if its a very small pot them take the opportunity to repot it too, it will be glad of some nice new compost and water regularly but don't overwater. They tolerate drought better than they tolerate over watering. You'll know if you've overwatered as the root ball will be wet and brown when you repot. In which case repot but reduce watering going forward.