C172 student pilot reported misapplication of brake rather than rudder on landing resulted in runway excursion.

Narrative

Solo flight under part 91; VFR flying conditions. A runway excursion occurred on Runway XX in ZZZ. Upon landing; I attempted to correct ground track with left rudder; but my foot slipped too far on the pedal; and I accidentally added left brake input. The result was a heavy left yawing motion on landing; an opposite right rudder was applied; however the forces weren't enough to overcome the already left facing aircraft. The aircraft then entered the grass on the northwest side of Runway XX; rear elevator was added in order to decrease weight on the nose gear through the grass; the plane then stopped after entering Taxiway 1. The action of landing with brake input rather than rudder input caused the pilot flying to have control difficultly on landing; the inaction of adding corrections or performing a go-around resulted in the aircraft exiting Runway XX on a taxiway. After an engine shutdown; I performed a brief aircraft inspection; determining that the aircraft had no damages; I taxied the aircraft to the FBO.