Remove and discard skin from pork. Cut meat into 4 large pieces. Heat oil in a pressure cooker or frying pan over medium-high heat. Brown pork in batches on all sides, transfer to a plate.
Add onion to pan and cook for 5 minutes. Add garlic, chillies, paprika, fennel seeds and thyme and cook, stirring, for 1-2 minutes, or until fragrant. Add tomato, stock, vinegar, beans and thyme and cook for 1 minute. Season with salt and pepper. Bring to simmer.
Transfer pork and sauce mixture to pressure cooker. Close and lock the lid and cook on high for 25 minutes. Release pressure and open the cooker. Add capsicum, replace lid and lock. Cook on high for a further 25 minutes. Release pressure and open cooker. Transfer meat to a board and shred using two forks.
Meanwhile, simmer the sauce mixture for 10 minutes or until slightly thickened. Serve pork and a little sauce in tortillas with sour cream and coriander.