Howdy BensonP,
Well kinda being a "woodsy fella" myself here in the heart of the wood products world, what you saw was likely the result of a rapid change in humidity.... and to a certain extent it will stabilize, but... There's that "but" word again. Yeah, wood is seasoned ie: dried slowly to prevent splitting, and stored in relatively controlled environs after it is milled (especially for musical instruments). The killer is that most of your hardwoods will be somewhere around 7% moisture content when it is worked, and depending on where and how it is stored, sealed, & finished, may or not be tolerant to higher or lower humidity. Getting a bit damp will cause the wood to swell, and if it dries too quickly cracks may form. Dampening it up will close the crack, but it will still be there and reappear next time it gets dry.
Sorry it is not better news, but when we are making furniture and sometimes repair parts for instruments, we give our woods at least 90 days to acclimate before trimming and culling. Any part that is cracked is rejected as the damage is done and likely will creep and get worse over time. On the back of your guitar it may not be such a biggie, but the front where all the stress lives?
You might consider contacting Martin for information on the warranty if you purchased the guitar new, perhaps it missed getting sealed or something.
Take Care;
Doug
"what is this quintessence of dust?" - Shakespeare