".... should I just ignore it (since it is below the threshold)?"
You can simply ignore it since the income is indeed below the threshold and you do not need to include the small amount of income that was attributable to the estate as income on another return (the $600 estate exemption would cover that).
See https://www.irs.gov/instructions/i1041/ch01.html#d0e340
However, if you obtained an EIN, it would be advisable to file a return since the IRS will almost certainly be expecting one and, by filing the return as the initial and final return, the return will officially result in the termination of the estate as far as the IRS is concerned.
