Breaking in a Mattress?
I got a brand new Sealy Posturepedic mattress from Sleep Train. I think it’s called Highbridge, Highbrook, or something like that. Anyways they have a gracious return policy. I paid a pretty penny for it because it was comfortable and you get what you pay for.
Anyways onto the problem. I slept on it the first time last night and it felt great getting into bed. I woke up 8 hrs later and my lower back was a aching and my right side felt tender from sleeping on it. I had this issue sleeping on a firm mattress for 3 months (reason why I bought a soft/ new one). I can sleep in my guest room’s bed and wake up with no aches at all. The guest rooms bed maybe a tiny bit firmer than the new one.
Do I have to break the bed in? Is one nights sleep to quick to judge a new mattress? Will this minor ache go away once it broken in?
My plan is to sleep on it for a month and rotate the mattress mid way. But if a week goes by and the pain is worst i am returning it.

Breaking in a new mattress is actually a mattress breaking down. http://www.stlbeds.com/articles/2010/02/19/does-new-mattress-break-in/ It does however take approx. a month or more to get used to a new mattress. Think of it like getting used to a new pair of shoes or a new car.
One night is definitely too quick to judge a new mattress. Mattresses do have to be broken in, sort of like breaking in a new pair of shoes. I’d say give it a minimum 2-3 weeks before you come to a decision about whether you’re going to exchange/return it.
What most people don’t realize is that after being on the same mattress for 8-10 (sometimes even longer) years. Your body is going to have to adjust to something new. Which is very well where that soreness is coming from. Once your body has gotten used to your new bed, your pain should go away.