You could retake in theory, but most Admissions tutors for the purposes of University places and employers only look for the ''C'' in Mathsas very few people actually take statistics at this level,but if you're looking to do a Maths related course at degree level, then itmight be worth resitting, but a B is still a good grade. If you wanted to, then you could redo it along with your other GCSEs in the summer, but I would advise ensuring your other grades do not suffer as a result of this.
No doubt you'll have other replies very soon.
Best of Luck with your decision.