ALL tips are taxable income and should be reported on your return, regardless of size.
The tips should also be reflected in your quarterly estimates to avoid underpayment penalties.
From the IRS:
All cash and non-cash tips an received by an employee are income and are subject to Federal income taxes.
The requirements regarding reporting tips to employers don't apply to you since they are required for the employer to pay for medicare and SS on your behalf. Being self-employed, you will need to pay self-employment tax on that income instead.
There is no mention of a "threshold" below which you don't have to report tips. In fact, the example on this form uses only $18 in tips as an example:
Example. Ben Smith began working at the Blue Ocean Restaurant (his only
employer in 2022) on June 30 and received $10,000 in wages during the
year. Ben kept a daily tip record showing that his tips for June were
$18 and his tips for the rest of the year totaled $7,000. He wasn’t
required to report his June tips to his employer, but he reported all
of the rest of his tips to his employer as required.
Ben's Form W-2 from Blue Ocean Restaurant shows $17,000 ($10,000 wages + $7,000 reported tips) in box 1. He adds the $18 unreported tips to that amount and reports $17,018 as wages on his tax return.