Firstly, ifi were you, i would check in with a physiotherapist.
Then, i would implement some back extension movement where i am forced to use the erectors responsible for the thoracic spine - so i would try to improvise by lying with my belly on a chair, where one end of the chair touches my hip and the other end touches an inch below my nipples. Then its just stretching arms out forward and switching between trying to touch the floor with the chin and trying to touch the ceiling with the thumbs.
Next up, id hang in an inverted row position under a table and try to pull my shoulderblades together and low and then relax them again.
Id try to do both movements extremely slow and controlled for 5 minutes and would try to improve on repetitions each time.