It can still be considered self-employment even if it is a short-term service. The important question is whether this was connected to a college degree program, and was it arranged by the school and is a mandatory degree requirement. In that case, it is probably treatable as a fellowship for education, meaning it is taxable "miscellaneous" or other income, but not subject to self-employment tax.
If not a mandatory part of your education, then it still might not be considered self-employment. I can't find the specific document, but I recall something to the effect that, if this was a training position, and having you there was actually more of a burden to the company than a benefit, it can be considered other income instead of business income.
Lastly, if it was never your intent to earn a profit, and this work is not expected to lead to a regular job and was something you did for your education, you can call this hobby or other income, but this is the weakest of the 3 arguments. Because the income was reported on a 1099-NEC, the IRS will assume it was self-employment, and if you report it as "other" income, you will get an automatic letter asking you to pay self-employment tax or provide more details about why this is not self-employment.
To report as a business (self-employment, independent contractor) you enter as a 1099-NEC, fill out a schedule C for self-employment. You may be able to deduct business related expenses. You pay self-employment tax on the net profit, and you may pay income tax depending on your other income and deductions. To report as miscellaneous income, enter the 1099-NEC but answer all the test questions as no (not for profit, not like my regular job, will not do again, etc.). But be mindful that if you don't report this as self-employment, the IRS will probably ask you about it.
