Make it impossible to uncheck the selected checkbox

Hello!
How can I make so that after checking the checkbox, I can't uncheck it?

There's no functionality for that. Best I can suggest is use CB Conditional and apply a static condition to the fields self. This can be done using the below.

Display: Field conditional hide
Field: Custom > Value
Custom Value: [FIELD_NAME]
Operator: Equal To
Value: 1

Replace FIELD_NAME with the name of your field.

I tried to do it on your advice. After the suggested settings, I get the following:
1) Click Edit>Update Your Profile
2) Check the Checkbox
3) Click Update
4) Click Edit>Update Your Profile again
5) I see that the checkbox is hidden
6) Click Update
7) I See that the Checkbox has Appeared and the mark is removed.

The hidden checkbox is unchecked without authorization after updating the profile
PS: If this is important: Edit Style - Buttons

You'll need to turn off value resetting in CB Conditional > Parameters since it by default resets the value of a field if condition doesn't match. This could be a problem if you're other conditions in place that do need to reset though.