An income tax return for a trust (1041) is required to be filed if there is any taxable income or gross income of $600 or more. The $43, however, is less than the $100 exemption the trust would receive. Regardless, you can file a 1041 and pass the $43 through to the beneficiary.
No matter what, you need to consult with a tax attorney, or other tax professional, with expertise in this area who can actually review the terms of the trust itself.
You have not provided sufficient information regarding the trust at this point. For example, does the trust mandate that an actual trust be set up for the minor or just something like a UTMA account?
I'm sorry for your loss.
