The teenage Spain star won and converted a penalty to clinch a narrow triumph but hurt himself as he took it and was replaced before half-time.
Joao Cancelo also went off injured for a Barca team who moved nine points clear of Real Madrid at the top of the table with six matches remaining, including a Clasico on May 10.
“We have to win every game and seal La Liga as soon as possible, it was important to win today,” Pedri told Movistar.
“I hope (Lamine’s injury) is for as few weeks as possible. Tomorrow he’ll be tested and we’ll see what it is.
“I wish him the best of luck, and he should stay calm — he’s young and will surely recover well.”
Hansi Flick’s side, playing for the first time since their Champions League quarter-final elimination by Atletico Madrid last week, lacked their usual attacking spark.
Barca goalkeeper Joan Garcia saved well from Pablo Duran and Ferran Jutgla in the opening exchanges at Camp Nou.
With little between the teams it came down to Yamal’s fleet footwork to help Barca open the door.
The forward skipped into the box, exchanging passes with Dani Olmo, and was felled by Yoel Lago as he tried to evade the Celta defender.
Yamal beat Ionut Radu with a low penalty, with the goalkeeper diving the right way.
However he pulled up hurt immediately, calling for treatment and lying on the turf as his team-mates came over to celebrate.
The match was delayed for over 15 minutes because of a medical incident in the stands at the same time, and when Celta kicked off again, Yamal had been replaced by Roony Bardghji.
Barca battled through the second half without creating much until Ferran Torres lashed home with a volley from Pedri’s pass.
The Catalans’ joy was short-lived though as the goal was disallowed for a marginal offside call against the Spanish forward.
Former Barca defender Marcos Alonso smashed a free-kick into the wall as the hosts held on to claim three potentially vital points.
Defeat left Celta seventh and still hoping to qualify for European football next season.
“We were very good in the first half, we had chances and they didn’t have so many… but individual talent made the difference,” said Jutgla.
“La Liga is very competitive and we will fight until the end.”