pics attached.
guys, appreciate the immediate response. The wheels are on tight, I've checked that.
When I bought the truck I did notice some marks on the shock, but as the truck had just been serviced at the Ford dealer I didn't worry too much, though it might have been a one off thing.
The wearing of the exterior of the shock seems a lot worse now, I only noticed it this weekend as I had a pop out when accidently jumping/falling off an 8 foot dune. Luckily it was really soft sand, but still got the pop out.
I've been advised here by fellow truck owners it could be worn bushes or the wheels need to be aligned again. Which I will do this week.
Attached the pics now for you guys to see.