In a small bowl, combine the yogurt, sour cream and chipotle chiles. Cover and refrigerate until ready to use.
PREPARE THE FISH:
In a small bowl, whisk together the oil, lime juice, salt and pepper. Put the fish in a pyrex dish and pour the marinade over the fish fillets; let marinate for 20 minutes.
Remove the fish from the marinade and grill on a preheated grill or nonstick grill pan over a medium-high heat until cooked through, about 3 minutes per side. Set the fish aside on a plate for 5 minutes. Flake the fish with a fork.
ASSEMBLE THE TACOS:
Heat the tortillas on the grill or grill pan for 30 seconds on each side.
Top each tortilla with 1 tablespoon of the chipotle cream. Top with fish, cabbage, corn and cilantro; serve with lime wedges.
Notes
You can sub another white, flaky fish for the tilapia if you'd like (such as halibut).