Your snake is just fine.....and aspen is just fine as a bedding.

Newspaper and reptile carpet can have their problems too. I have had a ball pythons rip off a small piece of newspaper during constriction (the rat was under the newspaper corner) then proceed to eat the rat and piece of paper. I have also had a ball python miss a rodent when striking and get it's teeth caught in the reptile carpet until it jerked free.

There is no "100% carefree" substrate....and after all.... these guys don't eat off clean surfaces in the wild