Hello and thanks for the query
The problem you are facing is due the nerve injury
that has occurred due to the trauma you have faced. It is a good sign that the numbness
has improved immediately after the surgery. So there is every chance that you will get full movement of thumb but it will take its time as your surgeon has explained you. The nerve injury always take time to heal it depends on the nature of injury and its effect.
Do regular exercise as advised by your physiotherapist and surgeon. No additional exercise is needed. As you have undergone surgery 5 days ago there are limited exercise you can do but you can increase it as the time goes.