How much movement at the swingarm end? Check the swingarm pivot nut for correct torque, i.e. loosen it and re-torque it, does it still move/knock?
It's possible the bearings have become dry, due to a failed thrust/cover seal or lack of maintenance. If you're lucky and you've caught it in time a repack of grease and the seals are ok (check if they're dry/going brittle replace) you may get away with it, but it's also very possible they're shot and you'll have to replace the bearings and thrust/covers. You should be ok with the pivot shaft, but it's possible it's damaged too, depending how bad a going over with fine wet/dry may sort it, but if it worn by more than a few thou it's also buggered, if you use it and it's worn it will bugger the new bearings in short order.