You may carefully cutting down on the red arrow color (between white dot) about 2 cm.
And then try to ware if not yet to through your head you may cutting more for 1 cm. until your head can through to.
After that you may find a little cloth to cover at the edge of the shirt that you cutting and do needlework to prevent the edge unravel.
Use the same color thread and cloth or difference if you like and you may sewing buttons on clothes if you feel loose.
Hopefully that will go well