You need to give it time and invest in exercise often.
Atleast 5-8 times a day practise opening your mouth for five minutes each time. Forcefully press the upper and lower jaw upward and downward respectively using your index and thumb finger.
Use ice-cream sticks piled up. Each time increase the number of sticks.
It definitely will be a little painful but continue doing it.
2 finger opening in 12 days is a great improvement but you should atleast have a 3 finger opening
Next Steps
be patient, keep your will power at its peak, donot forget to exercise