The statement from Barça's website is this:
Following the 1-0 win at Villarreal, the Club Medical Services have released a statement regarding the conditions of Lionel Messi and Munir.
The former has pulled an adductor muscle in right hip, and precautionary measures will be required. Meanwhile, Munir has bruising on his right thigh. Tests on Tuesday should be able to determine the full extent of the injury.
The Argentinian played all ninety minutes of the win at El Madrigal, while Munir was on the field for 59 of them.
From what it seems, none of those injuries are serious, so there's no reason to worry.
Messi is most likely going to be left out of Argentina's squad that will play friendlies in the next two weeks, so he can fully recover from the contusion.
Munir's problem is minor, so his rehab process will be quick. Both are expected to play for Barça on the team's next Liga game, against Athletic Bilbao, September 13 at Camp Nou.