Scott,
Photographs would be helpful; we don't know how big the cracks are, where they are, what their direction is relative to the axis of the gun. So the suggestions you have gotten, while well-intentioned, are based up very little information.
It is not uncommon for wood stock blanks to swell and shrink due to the movement of moisture in the wood. Warps are not uncommon. The fact that you put the barrel in in the summer (humid) and now have this issue in the winter (dry) suggests that the wood might be moving due to changes in wood moisture content. Keep in mind that when the rifle is finished the stock beyond the entry pipe is only about 1/16th inch thick - the barrel supports (and protects) the fore-stock, not the other way around.
Assuming that the cracks are running along the length of the blank I would saw the blank down so that the sides are about 1/4th inch thick along the barrel, thicker along the bottom because you nave a ramrod and lower fore-stock thicknesses there. This will relieve tension between the warped wood and the barrel without losing wood that you will need to finish the gun. Then you can repair any residual cracks with a good wood glue like Tite-Bond. You don't need a glue that is stronger than the wood.
That's the best I can tell you with the info you have provided.
Good Luck.
Best Regards,
JMC
John Cholin