Self-employment (SE) tax liability is not reduced by nonrefundable credits. Nonrefundable credits only reduce income tax liability and will not reduce other taxes reported on Schedule 2 (Form 1040), such as SE tax.
In a tax return with both an income tax liability and one or more nonrefundable credits, once the credits have reduced the income tax liability to zero any remaining credit is either lost or carried forward to the next year. Whether a nonrefundable credit is limited to the current year only or can be carried forward depends on the credit.
It's important to remember that self-employed taxpayers are responsible for paying SE taxes on their earned income just as employers are responsible for withholding and remitting payroll taxes from their employees' income.
SE tax consists of social security and Medicare taxes. The SE tax rate is 15.3%, consisting of 12.4% for social security and 2.9% for Medicare. A self-employed person paying SE tax is paying into the Social Security system and is gaining quarterly credits in that system, just as an employed person is doing. If the self-employed person doesn't pay SE tax, they aren't gaining credits with Social Security and so will not receive Social Security when they reach retirement age.
Note: This is a general discussion on the relationship between nonrefundable credits and self-employment tax and is not intended as tax advice.
Additional Information:
Schedule SE - Self-Employment Tax
Desktop: Schedule SE - Self-Employment Tax
ProWeb: Schedule SE - Self-Employment Tax