IRS Tax Topic for underpayment of estimated taxes - https://www.irs.gov/taxtopics/tc306
If you didn't pay enough tax throughout the year, either through withholding or by making estimated tax payments, you may have to pay a penalty for underpayment of estimated tax. Generally, most taxpayers will avoid this penalty if they either owe less than $1,000 in tax after subtracting their withholding and refundable credits, or if they paid withholding and estimated tax of at least 90% of the tax for the current year or 100% of the tax shown on the return for the prior year, whichever is smaller.
Since the Self-Employment tax on the $3,500 of SE income will be less than $1,000 you should not have an underpayment penalty, assuming that is your only income for tax year 2023.
