The World Player of the Year limped off at halftime in Barca's 2-2 Champions League quarter-final first-leg draw away to Paris Saint-Germain on Tuesday and is doubtful for next Wednesday's return at the Nou Camp.
Local media reports had said he would be out of action for about three weeks.
"I will return soon, thankfully it was not so serious." Messi said on his Facebook page.
"We are so sorry for Masche [Javier Mascherano] we will give our support he returns as soon as possible."
His Argentine team mate, defender Mascherano, was carried off on a stretcher in Paris and has been ruled out for six weeks with knee ligament damage.
Messi is Barca's leading scorer with eight goals in the Champions League and 43 in La Liga this season, and is an ever-present figure in the side.
He is rarely rested and has been extraordinarily resilient to injury. The last time he was sidelined with a muscle injury was in November 2009 when he was out of action for a week, Barca said.
Barcelona host relegation-threatened Mallorca on Saturday holding a 13-point lead over chasing Real Madrid with nine games left to play.
Messi's absence will bring to an end his latest scoring feet of netting in 19 successive league matches, against every team in La Liga consecutively.
