A convenience store clerk in Brookline was injured Friday during an altercation with a customer who had a box cutter.Police said Jimmy Gaston, 25, of Boston, got into an argument with a clerk at the 7-Eleven at 870 Commonwealth Ave.A struggle ensued and the clerk suffered injuries to his head from a box cutter.Customers restrained Gaston until police arrived.The victim was taken to Brigham’s and Women’s Hospital with non-life-threatening injuries.Gaston was charged with assault and battery with a dangerous weapon.