Throwing the bib was a mistake, says Chelsea's Costa

English football giants' Chelsea's forward Diego Costa has admitted that he made a mistake by throwing his bib towards head coach Jose Mourinho, a few days back.

"The bib (incident) is in the past. I made a mistake, but my relationship with Mourinho is amazing, we get on really well. There are things you need to control, but the bib thing was an impulse," Costa was quoted as saying by goal.com on Thursday.

The Spanish international has just netted four times this season and he himself believes he needs to improve a bit.

"I have to improve a bit. The start of the season has not been good for me -- not in how I have played nor in goals," he said.

"I know I have to be better to go to Euro 2016 with Spain. I have to work hard and fight, but I know I have time to improve and I hope I will.

"The truth is Chelsea haven't been in a great moment, above all losing the other day in home. Today it was important to win to make the fans happy and to recover our confidence," Costa said after his side's 2-0 victory over FC Porto on Wednesday night in the European Champions League.

The 27-year-old clashed with Spain's captain Iker Casillas in the match, but the former said it was just a joke.

"Nothing happened with Iker, we just had a joke, there are no problems with him. How can I have problems with the captain of the Spain team?" he said.