England's Jos Buttler sustained a "small, stable fracture" of his thumb playing for Lancashire in their T20 Blast win over Worcestershire.
The 25-year-old wicketkeeper, who was overlooked for England's squad to face Pakistan in the first Test at Lord's, was struck by the ball while trying to stop a Luis Reece delivery.
He still scored Lancashire's fastest-ever T20 fifty, off just 20 balls.
Lancashire said the injury "will be managed conservatively".
The county have not put a timetable on his likely return to action.
Lancashire play Derbyshire on Wednesday in the T20 Blast and Buttler could play just as a batsman, with Alex Davies stepping in as wicketkeeper.
Buttler hit four sixes and seven fours in his 57 as the holders chased down their 199-run victory target in 18.1 overs at New Road.
His match-winning innings came three days after an unbeaten 73 in England's T20 win over Sri Lanka at the Ageas Bowl.