It is emergency- I can't fix the button soon then I will have buy a new gas stove. How to fix this? I pressed the edge of the button too hard when locked. We don't usually use the lock so it was a surprise to me.
An emergency would be if it was stuck on and you couldn't shut the gas off. This is an inconvenience.
These look like simple electronic buttons. Looks like the button has been pushed through the control panel. Its likely held in by little plastic clips.
If you are lucky, the clips aren't broken. You can disassemble the control panel and push the button back into place.
If the clips are broken, you can fix it properly with a new button (or possibly new control panel if they don't sell the buttons separately - still cheaper than a new stove). If you just want it fixed now, you can probably epoxy the button into place instead. Make sure the button itself still works before you do that.