gcse maths - resitting in year 13

will I be able to sit my maths in year 13 but also apply for uni? will unis accept me if the gcse maths is pending? I really don't want to do it this year as I just want to get good AS results without worrying about maths

Yes you can, if a better gcse maths is required they can make that condition as part of your offer. If you are sure you don't want to do it this summer, why not do it in November?

Thing is in worried because you apply for uni in November

The deadline for applications isn't in November, this year it was 15 January. November Gcse results were released on 11 January. It would be better to do the GCSE this summer in my opinion but only so you get it out of the way and can concentrate fully on A levels next year. As long as you have an otherwise strong application for the course that you want, universities will be ok with waiting for your GCSE maths result.