Heat oil in pressure cooker set to Sauté on Normal.
Cook onion with a pinch of salt in hot oil until softened, 3 to 5 minutes.
Stir garlic, tomato paste, chili powder, cumin, oregano, turmeric, and cayenne pepper with onion; cook, stirring frequently, until very fragrant and sticking to the bottom of the pot, 2 to 3 minutes; add bison and cook until completely browned, about 5 minutes.
Press Cancel on pressure cooker.
Stir tomatoes, beef stock, sweet potatoes, and bell pepper with the bison mixture.
Lock pressure cooker lid in place and set steam vent to Sealing.
Select Pressure Cook (Manual) and cook for 15 minutes on Low/High pressure.
Once the cooking cycle has completed, set steam vent to Venting to quick-release pressure.
Turn pressure cooker to Sauté mode and stir until desired consistency is reached. Serve with desired toppings.