There is a famous saying with bonsai - "one major offense per year". Generally this means if you do a major repot, you should wait to do a major pruning - because you want to give the roots a chance to recover before you stress the top of the plant, and vice versa. There are about a million exceptions to this rule that you will learn over time, and once your trees are more advanced you will be able to do an "easy" repot at the same time you do a "light" pruning, and there are times when you want to reduce roots and branches at the same time. But for young trees, trees that have just been collected, or trees that have just come from rootbound conditions, it is a good default rule to live by.
In most cases, with black pines that are in early development, you want to let them grow for a year or two, get really strong, and then prune them back. This will develop a thick trunk, and encourage back-budding. The key to black pines is that they are very apically dominant - they are much stronger at the top of the tree then the lower branches. If you just let a black pine grow, it will grow tall, fast, and the lower branches will weaken and die (since the tree no longer needs them) and once dead they are hard to replace because black pine almost never buds back on old wood. So you want to keep your lower branches maintained and not let them get too leggy or long, let a "sacrifice" branch grow like crazy for a few years (thickening the tree and increasing the root mass) and then you prune the sacrifice branch and the tree will shift all of that energy into the remaining branches. The lower your sacrifice branch the better, because you want the base of your trunk to thicken faster than the top of your trunk - giving your trunk taper and character.
In a nutshell, I wouldn't prune those trees this year because you just repotted them. I would, however, wire the trunks to introduce movement or else you will find yourself growing telephone poles