England wicketkeeper Jos Buttler is to have an X-ray after hurting his left hand during Lancashire's T20 Blast win over Worcestershire on Friday.
Buttler was struck by the ball while trying to stop a Luis Reece delivery.
But it did not stop the 25-year-old smashing Lancashire's fastest-ever T20 fifty, off just 20 balls, at New Road.
"I don't want to speculate, but it's a nasty knock. Once we get it X-rayed, we'll know," said Lancashire head coach Ashley Giles.
Buttler hit four sixes and seven fours in his 57 as the holders chased down their 199-run victory target in 18.1 overs.
His match-winning innings came three days after his unbeaten 73 in England's T20 win over Sri Lanka at the Ageas Bowl.
"He did make a comment that he doesn't use his top hand anyway," Giles told BBC Radio Lancashire. "He played beautifully. He now opens the batting as well. What doesn't he do?"