ESA ending and taxable income

Hello, I am wondering if anyone can help me. In January my ESA ended and Ive moved onto full contributory state pension (which I know is taxable). I recently received information from ESA saying my esa was taxable. I was paid just under 10k for this 24/25 tax year of which £0 was taxable. I also received a p45 which doesn't show any £ amounts for tax purposes. I have a small contracted out serps pension I would like to take as a lump sum and pay off my mortgage and trying to figure out whether to take now or after April 5th. Otherwise it is just state pension I believe for tax. I currently receive PIP but up for review and awaiting outcome. I have also claimed pension credit but that will depend on my PIP outcome as my state pension is higher than the pension credit qualifying £. Thank you in advance