Personal experience: give it a few days before doing any kind of medication.
Horses do hurt themselves from time to time and two days of a slight lameness does not automatically equal joint supplements or injections. He may have done something in pasture, or when he spooked, that is making him limp.
Also, have you checked his feet and shoes thoroughly? A loose nail or lite case of thrush can have the same affect, even on a problem leg. I'd investigate the injury thoroughly before I would start on any kind of supplement.
As far as the supplements go - my guy has a bone chip in his right hock and they don't seem to noticeably help one way or the other so I quit buying them after a couple of years. The vet has said we can do injections, but I'm waiting until he gets older, as the injections lose some of their effectiveness over time.
Personally, I've found that a good fitness routine and regular exercise (keep muscles good and fat to a minimum) are the best long-term treatment for long-term injuries or issues.