If you've already e-filed your tax return and it was accepted by the IRS, or if you mailed your tax return through the Post Office...then yes, you'll have to amend your tax return to include the income and expenses of the side job. The fact that you had more expenses than income is okay. This will produce a loss on your Schedule C and will reduce your wages from your main job. It is also okay that you didn't receive a 1099 for the side job.
In order to enter the expenses associated with the income, an upgrade to Turbo Tax Self Employed is necessary. Turbo Tax Premier does not support business expenses. The good news is that the cost of the upgrade could be considered to be a business expense to deduct on next years taxes (even if the business is not in operation, the cost of the upgrade is still deductible on next years taxes).