I purchased a Ryobi 36V lawn mower last year from Bunnings - however over time, the rear wheel has become increasingly unstable and wobbly, and I am worried that the wheel itself will break. I've had a look, and I seem to be unable to tighten the nut - can anyone give me any advice on what to do please?
Any help would be greatly appreciated.
you can see from the two images below how far the wheel 'wobbles'

Ryobi 36V HP Brushless 53cm Lawn Mower 6.0Ah Kit - Bunnings Australia