You are required to report and are subject to taxes on all earned income including wages, self employment and some catergories of investment, dividends and interest, just to name a few sources.
However, in so filing, you will establis if any taxes are due to the IRS or if any refund of withheld taxes are due to you.
If you do not file, how will you let the IRS know if you elected to take the standard deductions, etc.
Most likely, wiht an income of less than 7,000, you will not have any taxes due, and you would get back any taxes that were withheld.
However, consider also, that if this is self employment income, you will at least owe 15.3% self employment tax. Self Employment tax is the tax that you pay that is SS and MC for self employed persons.