I was thinking of flash as well when trying to assess, and its not pessimistic, its realistic. I don't know if he's lame as I've not seen him do more than 3 steps, but I would be able to see in that if he was badly lame which he's not. I've emailed my vet to ask if she thinks a visit would be in order.
Best news is that if it is that, a few weeks rest and the correct management- there’s every possibility that he’ll be absolutely fine. Flash has had such an uncomplicated recovery. If I could bottle it and sell it as a certainty I’d be a squillionaire.