Injured thumb won't bend now that it has healed

[Hewzee]

2 months ago I mangled the front of my left-hand thumb on a table saw. It was quite a mess but the damage was superficial and several stitches and weeks later it looks almost good as new. There is still scar tissue at the front and the top section is still numb.
The only problem is that after being bound up in bandages for the entire time, I now can't bend it.
I think I still have several weeks before the front is fully healed but the skin/ tendons at the back of the thumb are so tight that I can't bend the thumb forward. I can move it a little bit. At rest it curves outwards- further than I can bend my good thumb on my right hand back. Even with help I can't bend the left thumb. As I said above, it is extremely tight at the back, the knuckle is smooth compared to the dried prune-like loose skin on the right thumb knuckle.
Are there any exercises I can do to improve the range of movement?