Chronic anxiety/old mattress

I woke up a few months back with a firm mattress digging into my backside. It was 5 years old and the sprigs were popping up. I also have chronic anxiety so I worried I damaged a nerve. Checked with a nurse they said do exercises im quite lazy and hope it will go away it’s self. I get other pains which usually go can it take long to heal? Was it the mattress? I can’t think of anything else but when I woke i Felt pain when I stood or sat down but now the pain is less mostly notice it when sitting upright does that mean it’s improving? I did buy a new mattress but it was a soft one quite cheap so that may not help too as it’s not an expensive one. The pain is like a dull ache like I have sat down too long or friction feeling?