With out sounding like a total newbie here, I'm hoping someone might be able to throw me a bone on a recent issue.

I have a giant 29er fitted with the standard schwalbe nobby nics that came with the bike.
Today I went to rotate the tires front to rear, and once inflated both are incredibly out of round, and seem off centre of the rim.

I deflated and re-inflated them and tried to manipulate the way they sit on the rims but without much luck.

I've changed tires a million times without issue, however this is the first time on the 29er.

Am I missing something?