The controversial sign in question reads, "F (expletive) Trump and f (expletive) you for voting for him."
"I have received numerous calls regarding the offensive display on this truck as it is often seen along FM 359," Nehls wrote on Facebook. "If you know who owns this truck or it is yours, I would like to discuss it with you."
During the press conference, Nehls said he had no regrets about the controversial Facebook post.
"Our prosecutor has informed us she would accept disorderly conduct charges regarding it, but I feel we could come to an agreement regarding a modification to it," he wrote.
ABC7NY's sister station ABC13 first tracked down the driver of the pickup truck. Karen Fonseca said she put the custom-made graphic up about 11 months ago.
She said her family is expressing their First Amendment rights and voicing their dissatisfaction with President Donald Trump. Fonseca said she's surprised Nehls couldn't reach her. She's open to sitting down with him.
She insisted that she has no intention of removing the sign.
"It makes people happy," she said. "They smile. They stop you. They want to shake your hand."
Fonseca said she's most at odds with the president about his proposed border wall.
She said people tell her they "wish they had the guts" to put up a similar sign on their vehicle.
The American Civil Liberties Union responded to Nehls' Facebook post.
"No Sheriff Nehls, you can't prosecute speech just because it contains words you don't like," ACLU said.