you need to give some pics. there is two ways it could have stripped. 1 the actual outer diameter is stripped so the socket just slips. or 2 the threads are stripped so when you loosen it just spins and will not spin off. in both cases just cut the nut off you dont need the old axle and you dont need the nut. dont cut the axle end off. just cut a groove in the top of the nut and in the bottom. so that you can split it into two pieces.