By Matthew Cooper Mikel Arteta has admitted Arsenal face a difficult challenge to end the season on a high following their Champions League exit. The Gunners were beaten 3-2 on aggregate in their quarter-final clash against Bayern Munich, with Joshua Kimmich scoring the winning goal in the second leg. The defeat comes just days Arsenal’s Premier League title hopes took a major hit as they lost 2-0 to Aston Villa. That result leaves them two points behind Manchester City with just six games to go and Arteta has urged his players to “go through the pain tonight” and bounce back for their trip to…