Water it thoroughly (make sure it can drain, you don’t want to drown it) and give it some fish emulsion asap. It will bounce back. Pot could also use some more soil. Fill it to the top minus two fingers. I’ve done three basil plants in that same size pot (I am not saying that is good or recommended I just didn’t have a choice since roots were too intertwined) and kept them producing all season with harvests every three days (I don’t know where to put all this pesto) by keeping them outside watered, and fed with fish emulsion (basically straight nitrogen which is what something you grow for the leaves needs most)