Did you pour it slowly through the skimmer? If you did, and it still plugged the impeller, I'm amazed. Powdered CYA will plug up, but I've never seen it do so like that.

BTW, if you add borax, make SURE you pour it in slowly -- it WILL plug things worse than CYA, if you get ahead of the water flow.

Back to your pump: you can replace the seal and impeller, or your can wait a couple of days -- pump running! -- and see if it will dissolve.

Ben