We generally recommend pruning in late winter when the tree is dormant. Your tree can be pruned now, but each cut provides a new entry point for reinfection. If you see a week in the forecast without rain, you could consider pruning out the galls now and destroying the material you pruned out. Unlike in winter, it would be good to sterilize your pruning tools between cuts with something like a bleach solution, if pruned during the growing season. The galls have probably already released most of the spores they will be releasing, but they can continue to release spores and infect tissue during wet weather until the new shoots have matured. Either way, black knot is very aggressive, and you will have new galls apparent by next spring, in wood that has been infected this spring. 

The easiest course of action would be to wait until late winter to prune, and to apply a fungicide next spring, as soon as the flower buds begin to open, repeating as necessary. Note that only some formulations of lime sulfur are certified for organic use, and copper and sulfur-based fungicides are not as effective as other fungicides. It wouldn't hurt to apply a fungicide now, but it is likely that most of the damage has been done for this year. Once you have pruned out most of the diseased wood in winter, you can continue to prune out any diseased wood that becomes apparent in the spring, trying to remove it before the fruiting bodies release their spores.

More details on pruning and what to apply and when are in the following publications:

https://www.canr.msu.edu/news/controlling_black_knot_in_michigan

https://extension.umn.edu/plant-diseases/black-knot#using-fungicides-1170312