Hi,
From the information I'm not too sure if you are UK Citizen but if you were you would qualify for a tax allowance. Self-assessment is only viable if you are not an employee of your business i.e if you are a sole trader as you say you are.
Based on these assumptions, you would be taxed on any taxable income, less allowable costs after the tax allowance. You would also have to pay Class 2 & 4 NI contributions depending on how much profit you actually made.
Therefore your business (as sole trader) is getting taxed via yourself. Hope this is clear, if not don't hesitate to ask any questions.
I can also submit, your tax return and send you a set of accounts if you provide me with all the necessary details.
Regards