The game between Sevilla and Barcelona was a good opportunity for a palyer like Sergio Ramos. He played for Real Madrid for years and during that time he played in many games against Barcelona.
His return to Sevilla should be a happy ending for his career and for Sevilla as one of best players grown up by them finally came home.
Since Sergio Ramos left PSG people have thought he is far from his good form and that he could prove himself in this game but this own goal had certainly a negative effect.

It is bad because it caused a loss for Sevilla but the season is long and no shame when Sevilla lost against one of strongest clubs in La Liga, Barcelona. Without that own goal, they could lose it in another way when Barcelona create more pressure.
Not only he will pick form, but the Spanish La Liga is a place where he spent quite a good number of years playing for Real Madrid, and he has become familiar with the league, therefore adapting is not going to be a thing of worry at Sevilla he just need more time to blend in with the team's pattern of play. Every player makes a mistake and this own goal of Ramos is not the first of its kind.