No, if just "a shirt" rather than multiple shirts that seems de minimis. Unless you are selling these in volume, and in two days no one will care, as it will be too late. People will likely be buying Bronco shirts then.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.
Everyone can lawfully affix onto their own shirt any words, phrases or designs they want and then wear that shirt in public so long as what's displayed is not obscene or otherwise unprotected by the First Amendment. This is true even if what's displayed is protected by someone else's copyright or serves as someones trademark. As for copyright, one shirt is de minimus copying and, as for trademark law, because the shirt is not in commerce that law has nothing to say about the matter.
The above response is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.