Myler was forced off during his comeback on Saturday as Warrington earned a 40-30 win at Castleford Tigers in the Super League.
"He tweaked it and felt his knee wasn't fantastic," Smith told the Warrington Guardian. "But like we're telling him, be optimistic until you find out otherwise.
"He felt a twinge but it might settle down. It might just be a part of the healing process - sometimes that happens. We'll be checking him out over the next day or two."
Warrington return to Super League action on Saturday when they host the Wakefield Trinity Wildcats.