Welcome Bob. I read your todays training post as well. All I can advise ( and I am injured too!!) is take it steady. Running does take a bit of time to adjust to and as a cyclist you might have strong quads, but running is very complex in the muscle groups used and the inter relationship of those muscle groups. By not all working together in harmony, injury or a feeling of uncomfortableness occurs easily. I should work on glutes, core strength and hip flexors as much as just crushing your thighs on a down hill!
I would really build distance slowly and methodically. A 30 KM race so soon might be counter productive. Perhaps better to miss it for now?